THE ROLE OF HYDROGEN CYANIDE IN CHEMICAL EVOLUTION 
by 
Rafael Navarro- Gonzalez 
Dissertation submitted to the Faculty of the Graduate School 
of The University of Maryland in partial fulfill~ent 
of the requirements for the degree of 
Doctor of Philosophy 
1989 t . \ 
Advisory Committee: 
Professor Cyril Ponnamperuma, Chairman/Advisor 
Professor Norman J. Hansen 
Professor Joseph Sampugna 
Professor Raj K. Khanna I 
Professor Joseph Silve \r  man 
Doctor Mitchell K. Hobish 
? Copyright by 
Rafae l Navarro- Gonz.:1lez 
1989 
ABSTRACT 
Title of Dissertation: THE ROLE OF HYDROGEN 
CYANIDE IN CHEMICAL 
EVOLUTION 
Name of degree candidate: Rafael Navarro-Gonz~lez 
Degree and year: Doctor of Philosophy, 1989 
Dissertation directed by: Cyril Ponnamperuma, 
Professor and Director 
Laboratory of Chemical 
Evolution, Department of 
Chemistry and Biochemistry 
Two maJor research areas are investigated: The 
electrosynthesis of hydrogen cyanide; and the role of 
cyanocomplexes in the free- radical oligomerization of 
hydrogen cyanide. 
The electric discharge production of hydrogen 
cyanide from a simulated primitive atmosphere composed 
of methane, nitrogen and water vapor was investigated. 
The radiation chemical yield {G) of formation of HCN 
was determined to be 0.26. A free radical mechanism 
was proposed to account for the observed chemical 
changes. Computer simulations of the reaction 
mechanism could effectively model the early stages of 
electrolysis of the gas mixture, and permitted the 
estimation of the rate of electrosynthesis of hydrogen 
cyanide under various atmospheric conditions . 
The possible role of cyanocomplexes of transition 
elements on the free- radical oligomerization of 
hydrogen cyanide was investigated. Aqueous, oxygen-
free, dilute solutions of hydrogen cyanide and hexa-
cyanoferrate(II) or (III) were submitted to various 
doses of gamma irradiation. The presence of either 
cyanocomplex led to a significant decrease in the rate 
of decomposition of hydrogen cyanide. The major 
products were ammonia and carbon dioxide . Computer 
simulations of these systems permitted the elucidation 
of the reaction mechanism and the derivation of rates 
of reactions of free- radicals with the cyanocomplexes. 
The results obtained provide an insight into the pos -
sible role of cyanocomplexes of transition elements in 
chemical evolution. 
ii 
DEDICATION 
To my wife, Fabiola Aceves - Diaz, my son Rafael 
Navarro-Aceves, my mother, Carmen Gonz~lez de Navarro, 
and all members of our families. 
To the memory of my fath e r, 
Rafael Navarro- Contreras 
1932- 1985 
lll 
ACKNOWLEDGEMENT 
I am especially indebted to my advisor, Professor 
Cyril Ponnamperum~ for his constant support and 
encouragement throughout this study . He fostered 
creativity in my research by providing right degree of 
autonomy. I am thankful to Professor Joseph Silverman 
for a] lowing me have complete use of his ionizing 
radiation facilities, and to his graduate students 
Byron Lambert and Fuh - Wei Tang for their constant as -
sisLance during the irradiation of samples. I 
appreciate the great interest and help of Dr. Yasuhiro 
Honda during the development of the dosimetric methods 
and preparation of samples for electric discharges. I 
am also very thankful to Dr . Mitchell K . Hobish for his 
great inte rest and help at severa] stages in this 
study. 
I am indebted to my Mexican advisor, Professor 
Alicia Negr6n- Mendoza, Chairman of the Chemistry 
Department of the Institute of Nuclear Sciences, 
U.N.A.M . , for her constant interest and support 
throughout this study; I am thankful to Professor 
lV 
Murcos Rosenbaum P., Director of this Institute, f o r 
his interest and advises during my academic training at 
Maryland. I conducted a portion of this work in their 
Institute , and am grateful for their consideration t o 
us e th e ionizing radiation sources and the laboratory 
fa c j] i1,jes durinc- my short stays at Mexico City. I 
want to acknowledge a fellowship from The National 
Autonomous University of Mexico (U.N.A.M.) during my 
graduate studies at Maryland. 
I wish to thank all members of the Laboratory of 
Chemical Evolution for providing a friendly and scien-
tjfic atmosphere. 
Finu]ly to my wife, Fabiola Aceves - Diaz, and my 
sun Rafael Navarro- Aceves, for their constant 
encouragement and patient endurance, I am grateful in 
me asure beyond words. 
College Park, Md Rafael Navarro-Gonz~lez 
Spring, 1989 
V 
TABLE OF CONTENTS 
Section 
List of Tables viii 
List of Figures ix 
Chapter 1 THE ABIOTIC CHEMISTRY OF HYDROGEN 
CYANIDE 1 
1. 1 Introduction 1 
1. 2 Abiotic synthesis of HCN 4 
1. 3 Distribution of HCN 20 
1. 4 Formation of biomolecules from HCN 26 
1. 5 Research objectives 55 
Chapter 2 EXPERIMENTAL PROCEDURES 58 
2 .1 General 58 
2.2 Preparation of electric discharge 
samples 59 
2.3 Preparation of ll' - irradiated samples 62 
2 . 4 Irradiation of samples 64 
2 .5 Control Experiments 75 
2.6 Analyses of samples 75 
2.7 Radiation chemical yields: G 88 
vi 
2 . 8 Computer simulation of the chemical 
systems 89 
2.9 Presentation of data 98 
Chapter 3 ELECTROLYSIS OF A SIMULATED PRIMITIVE 
ATMOSPHERE. THE SYNTHESIS OF HYDROGEN 
CYANIDE 99 
3.1 Introduction 99 
3.2 Dosimetry of high voltage electric 
discharges 102 
3.3 Electrolysis of gas mixture 122 
3. 4 . Conclusions 152 
Chapter 4 THE EFFECT OF CYANO COMPLEXES ON THE 
FREE- RADICAL OLIGOMERIZATION OF HYDROGEN 
CYANIDE 156 
4. 1. Introduction 156 
4 . 2 The ~-irradiation of aqueous 
hexacyanoferrate(II) 158 
4 . 3 The b - irradiation of aqueous 
hexacyanoferrate(II)-HCN mixtures 174 
4 . 4 The 'o' - irradiation of aqueous 
hexacyanoferrate(III)-BCN mixtures 196 
4 . 5 The effect of cyanocomplexes in the 
free - radical oligomerization of HCN: 
Implications to chemical evolution 210 
vii 
4.6 Conclusions 217 
Chapter 5 GENERAL CONCLUSIONS 219 
5.1 Electrolysis of a simulated primitive 
atmosphere: The synthesis of hydrogen 
cyanide 221 
5.2 The effect of cyanocomplexes on the 
free - radical oligomerization of 
hydrogen cyanide 224 
REFERENCES 227 
v i ii 
LIST OF TABLES 
Number Page 
1.1. Estimated productions of HCN 21 
1. 2 . Initial Radiation Chemical Yields 40 
1. 3 . G 0 of formation of amino acids 46 
1. 4 . Chemical Equations used in 53 
1.5 . Percent Relative Rates of 55 
2 . 1. Sensitivity factors for ions in 77 
2 . 2 . Slopes (m) of calibration 87 
2 . 3 . Radiation and molecular product 91 
2 . 4 . Hydrogen atom reactions with 92 
2 . 5 . Hydrated electron reactions with 93 
2 . 6 . Hydroxyl radical reactions wi th 94 
2 . 7 . Miscellaneous reactions with 94 
2.8 . Relevant reactions in the fricke 96 
3 . 1. Initial chemical yields {G 0 ) in 134 
3 . 2 . Predicted radical and molecular 139 
3.3 . Estimated productions of HCN in 151 
4.1. Initial chemical yields {G 0 ) of 191 
4 . 2. Initial chemical yields {G 0 ) of 206 
4 . 3 . Initial radiation chemical yields 210 
ix 
LIST OF FIGURES 
Numbe r 
1.1. Formati on of DAMN : Initial Ste p s 27 
1. 2 . Mechanism of Adenine Synthes i s 32 
2. 1. Electric Discharge apparatus 60 
2.2. Preparation of Oxygen-free 62 
2. 3. Energy De pendance of the 67 
2 . 4 . Schematic Representation of 68 
2. 5. Experimental Layout for Measuring 71 
2 . 6. Me asurement of Heat Generation by 72 
2. 7 . Dose dependance of temperature in 74 
2 . 8 . Calibration Curve for the 78 
2. 9. Calibration Curve for the 78 
2 . 10 . Computer Simulation of the Fricke 97 
2 . C 1 o1 m. puter Simulations of the Effect 
98 
3 . 1. Time dependence of the 
104 
P
3 ea. k2 -. to- Peak and Zero- crossing 
107 
The Effect of Resistance 109 3 . 3 . 
Sch
3 . 4 . ematic Representation of 
110 
The Effect of Res 111 3 . 5 . istance of R:s on 
Dependence of the 
3 V. 6 o. l tage (a) and 
112 
Pressure Depen
3 d. e7 n. ce of Voltage 
113 
3 T. e8 m. perature Increase as 
1
a 1 6 
Tem
3 p. e9 r. a ture Increase as 
1
a 2 0 
X 
3. 10. Dose De p e ndance o f the 123 
3.1 1 . Dose De p endance o f the 124 
3. 12 . The Effect of Dose on the 125 
3. 13. The Effect of Dose on the 127 
3. 14. Gas Chromatogram of DNPH 128 
3. 15. Mass Spectra of DNPH Derivatives 129 
3. 16 . Dose De p e ndance of the Formation 131 
3. 1'7. Ef f ect of Dos e on the Formation 132 
3. 18 . Dose De pendance of the Chemical 133 
3. 19 . Computer Simulations of the 145 
3.20 . Computer Simulat ions of the 146 
1. 1. Decomposition of 160 
4 . 2 . Dose dependance of the 162 
4 .3. Variation of pH with irradiati on 162 
4 . 4 . Extinc tion coe ffi c ient of 163 
4 . 5. Dose dependance of the 165 
4 . 6 . Computed trends for the format ion 168 
4 . 7 . Computed trends for the formation 170 
4 .8. Dose dependance of the 173 
4 . 9 . Variation of pH as a function of 175 
4 . 10 . Decomposition of HCN during the 178 
4 . 11. Formation of hexacyanoferrate 179 
4 . 12 . Formation of molecular hydrogen 180 
4 . 13 . Computer simulation for the 181 
4 . 14 . Formation of CCb during the 182 
4 . 15 . Formation of NH3 during the 182 
? 
Xl 
4. 16. Gas chromatograms of DNPH 185 
4. 17 . Electron impact (a) and chemical 186 
4. 18. Formation of formaldehyde as a 187 
4. 19 . Gas chromatograms of 188 
4. 20. Dos e dependance of the formation 189 
4. 21. El ectron impact and chemical 190 
4.22. Dose d ependence for the formation 193 
4 . ?.3. DPpendance of the decomposition 194 
4.24. Ga s chromatograms of acids formed 195 
4.25. Decomposi tion of HCN in solutions 197 
4. 2G. Decomposition of hexacyanoferrate 199 
4.27. Formation of molecular hydrogen 200 
4.2D. Computer simulation fur 200 
4 .20. Formation of carbon dioxide 201 
4. 30. Effect of dose on the 202 
4 . :H. G~s chromato~ram of DNPH 203 
4.32. Electron impact and chemical 204 
4. 3?.. Dose dependence for the formation 204 
4.33. Gas chromatograms of acids methyl 205 
4.34. Dose dependance of the formation 207 
4. 3!J. Dose dependance of the formation 208 
4.37. Dependance of the rate 214 
4.38. Dependance of the rate 215 
4.39 . Dependance of the rate 216 
1 
CHAPTER 1 
 CHEMISTRY OF HYDROGEN CY
ANIDE 
THE ABIOTIC
1.1 Introduction 
 scenarios of the origin 
of life on Earth 
Modern
sed on ideas generated in
dependently by Oparin 
are ba
cording to these authors 
(1924) and Haldane (1929)
. Ac
pearance of the first liv
ing cells was preceded 
the ap
accumulation of organic c
om-
by abiotic syntheses and 
mplexity on the primitive
 Earth . 
pounds of increasing co
nd 
These compounds were ess
ential for the origin a
 
lution of phase- separated
 systems that eventually
evo
ng 
to the emergence of the f
irst populations of livi
led 
2; and Haldane, 
cells (Oparin, 1924, 1938
, 1957, 197
1938). 
g-
The earliest published ex
periment expressly desi
 of organic com-
nated as demonstrating th
e formation
mosphere was 
pounds from a hypothetic
al primitive at
2 
that by Groth and Suess (1938). They exposed a C<k -
EkO gas mixture with ultraviolet light at 147 nm, and 
identified formaldehyde and glyoxal as products. These 
results were interpreted as "giving an explanation for 
the formation of certain carbon compounds that were 
probably prerequisite for the appearance of life" 
{Groth and Suess, 1938). Later, Calvin and coworkers 
{Garrison et al., 1951) simulated the atmosphere-hydro-
sphere interface, by irradiating with a-rays an aqueous 
solution containing ferrous ion in equilibrium with a 
CO:z - fb gas mixture. Formaldehyde, formic acid and 
succinic acid were identified among the products. 
Shortly after, Miller (1953, 1957a,b) reported the 
synthesis of amino acids such as glycine, alanine and 
B- alanine, among others, from the electric discharge of 
a CH4-NH3-Ek-EhO gas mixture. Based on the observa-
tion that HCN and aldehydes were formed in thP- early 
phase of the experiments, Miller suggested that a-amino 
acids were formed by the Strecker mechanism {Miller, 
1957b), which consists of the condensation of HCN, 
RCHO, and Nfb (Reaction 1.1), followed by hydrolysis of 
the a -amino nitrile (Reaction 1.2): 
RCHO + Nfb + HCN RCH(NH:z )CN + IkO ( 1. 1) 
3 
RCH ( N~ ) CN + 2E-b 0 RCH ( Nfb ) COz H + NH"3 ( 1. 2) 
The first direct evidence of the possible impor-
tance of HCN in chemical evolution was indicated by the 
studies of Oro and coworkers, who found that adenine 
{Oro, 1960, Or-6 and Kimball, 1961) and amino acids such 
as glycine, alanine, and aspartic acid (Oro and Kamat, 
1961) were formed when an aqueous concentrated ammonia -
cal solution of HCN was heated. Such results were not 
only confirmed, but also the number of identified 
products was extended to include formic acid, urea, 
hypoxanthine (Lowe et al., 1963), and several other 
amino acids (Lowe et al., 1963, Matthews and Moser, 
1966) . 
These findings have such a significant impact in 
understanding the abiogenesis of biological precursors 
from simple molecules, that a reexamination of the data 
was suggested by Sidle (1967) to ensure that these were 
not due to low level contamination from the reagents 
and/or the environment. Over hundred scientific ar-
ticles published in the last two decades have not only 
demonstrated the versatility of HCN in promoting syn-
theses of a large array of biologically important com-
pounds, but also contributed to a profound understand-
ing of the chemistry involved (see, for instance, 
4 
Ferris and Hagan, 1984, and references therein) . 
This chapter reviews the current status of studies 
of the abiotic chemistry of hydrogen cyanide, and 
directs attention to areas where further research is 
needed. The material examined below has been grouped 
into three major areas of research; these consist of 
the synthesis {section 1.2) and the distribution {Sec-
tion 1.3) of HCN in the primitive Earth, and the 
chemistry involved in the formation of biomolecules 
using HCN as the starting material {section 1.4). 
Particular emphasis was given to include reaction 
mechanisms, chemical yields of products, and kinetic 
data in order to get a quantitative perspective of the 
possible significance of HCN in the process chemical 
evolution that preceded the appearance of life on 
Earth. The last section (1.5) on this chapter 
introduces the research objectives of this disserta-
tion. 
1.2 Abiotic synthesis of BCN 
HCN has been obtained in a number of studies in 
abiotic chemistry. The first investigations utilized 
5 
highly reducing atmospheres of different ratios of CH,. 
and Nfh in the presence or absence of Ek and/or EkO. 
These stud ies d e monstrated that the prcxiuction of HCN 
could be initiated by ultraviolet light (Ponnamperuma 
et al ., 1963; Fe rris and Chen, 1975; Toupance et al., 
1977; Ra ulin et al., 1979; Bossard and Toupance, 1980), 
electric discharges (Miller, 1957a; Ponnamperuma et 
al., 1969; Yuasa and Ishigami, 1975; Toupance et al., 
1975), heat (Harada and Fox, 1964; Koberstein, 1973), 
shock waves {Bar- Nun and Shaviv, 1975), and ionizing 
radiation (Palm and Calvin, 1962). 
Thes e studies are now considered of little signi -
ficance to the primitive Earth scenario because 
ammonia , if present, was probably in small abundance 10 
the atmosphere since it is extremely soluble in water 
(Bada and Miller, 1968). In addition, the studies of 
Ferri s and Niccxiem {1974), and Kuhn and Atreya {1979), 
indicate that if NH~ was present in the atmosphere, it 
would have been immediately photolyzed to N2 . On the 
other hand, the concentration of Ek in the primitive 
atmosphere must have always been small because of its 
fast escape from the Earth's gravitational force 
{Maurey et al., 1981). 
On the basis of the previous discussion, an atmos-
6 
phe r e composed mainly of methane, nitrogen and wat er 
vapor is now consid e r e d reasonable for the initial 
stages of the hi s tory of the Earth (Ferris and Chen , 
1975; Bossard et al . , 1982). Th e form a tion of HCN from 
t h ese g a ses has also been demon s trate d . A mixture o f 
CU,. and N:z in the presen ce or aosenc e of fb O has been 
e x posed t o uJ t raviolet l i g ht (Dodonova , 1966), elec tri c 
d ischarges (Sanchez et al., 1966; Toupance et al . , 
1975; Kobayas hi and Ponnamperuma, 1985b; Stribling and 
Mi ll e r, 1987), shock waves (Rao et al . , 1967) , and 
ion i zing radiation (Zhdam i rov et al., 1971; Bal esti c , 
197 4) . Addition o f fkS (Raulin and Toupance, 19750) or 
fk (Striblin~ and Miller, 1987) to the rea ction mixture 
leads to a significant decrease 1n the electric dis -
charge - driven production of HCN ; howeve r, these gases 
probably did not affect the synthesis of HCN in the 
primitive atmosphe re since fb was rapidly lost (Maurey 
et al . , 1981), and fbS seems quite unstable in models 
of pr i mi tive environments (Raulin and Toupance, 
1975a, b) . 
Evo 1 ut ion of the atmosphere from C~ - N:z - fb O to 
CO- N2-fkO and/or to CCk - N:z-fbO likely occurred rapidly 
(Levine, 1982; Levine et al., 1982); however, the dura-
tion of this process is unknown (Ferris and Hagan, 
1984) . Photochemical considerations indicate that 
7 
me thane could have been efficiently polymerized; 
McGovern (1969) estimated that such a process would 
have o c curred in 50- 100 million years, while Lasaga et 
al., {1971) estimated its duration in 1- 10 million 
y e ars. Levine (1982) has shown that photodecomposition 
of me thane depe nds on altitude, be ing v e ry un s tabl e at 
th e top of the atmosphere { t i1 , ~.~? 4 days), and gu i te 
s table at the surface of the Earth (approaching an 
infinitely long lifetime ). 
The formation of HCN in a mixture of CO- N2-EbO 
that was subjected to electric discharges has been 
r ecently r e ported by Stribling and Mill e r (1987). They 
found that the yield of formation of HCN was at l e ast 
an order of magnitude less than that obtained under 
s imilar conditions when CO was replaced by CH4 (Stri -
bling and Miller, 1987). Its yield could be increased 
if f b wa s added (Abelson, 1966; Stribling and Miller, 
1987); however, the presence of H2 in the primitive 
atmosphere is less likely, particularly at this stage 
{Mourey et al., 1981). The synthesis of HCN from CO-
Nfh mixtures exposed to ultraviolet light (Ferris et 
al., 1974a), and clay-minerals at high temperatures 
{Fripiat and Cruz-Cumplido, 1974) has also been 
reported, although are of little significance to the 
primitive Earth scenario based on the previous discus-
8 
sion {see page 5, this dissertation). HCN is not syn-
thesized from CCk-tb-EbO mixtures exposed to electric 
discharges according to Stribling and Miller, 1987. 
The only synthesis of HCN reported from such a mixture 
is from the work of Bar-Nun and Shaviv {1975), using 
shock waves. 
Based on the above results, it seems reasonable to 
conclude that the maJor production of HCN occurred when 
the primitive atmosphere was mainly composed of CH..-tb-
fbO. Therefore, a detailed analysis of the experiments 
utilizing these gases is important to get a better 
insight of the abiotic synthesis of HCN. 
1.2.1 Photolysis 
Nitrogen is sufficiently stable that its photo-
lysis is negligible, and generally only participates in 
photochemical reactions as a third body (Canuto et al., 
1983; Yung et al., 1984). Methane is photochemically 
reactive in the vacuum UV. Its absorption spectrum is 
a continuum beginning at about 145 nm, with two maxima 
in the absorption curve centered in the region between 
100 and 80 nm; there is no minimum at any wavelength 
down to 0.25 nm (Sun and Weissler, 1955; Ditchburn, 
9 
1955). Th e photochemical decomposition of methane has 
been studied in detail and its photo-dissociative chan-
nels as we ll a s their quantum yields 1 at 121 . 6 nm are 
indicated in reactions 1.3 through 1.7 (Gordon and 
Ausloos, 1967; Rebbert and Ausloos, 1972; Slager and 
Black, 1982) . 
Cfh? + H? ( 1. 3) 
C.Ek: + fb cfi =0. 580 ( 1. 4) 
UV 
CH.,. Cfb : + 2H? cfi =0. 510 ( 1. 5) 
. - CH : + fb + H? cf, =0. 060 ( 1. 6) 
. :C: + 2.Ek cfi =0. 004 ( 1. 7) 
Re a c tions 1 . 4 and 1.5 are the principal photodis -
sociative channels; reactions 1.6 and 1.7 are minor 
pathways, and reaction 1.3 is the least important 
{Slager and Black, 1982). The major products from the 
other hydrocarbons such as C2H.,., C2Ek are also formed 
but in low yield {Mahan and Mandal, 1962; Magee, 1963; 
Braun et al . , 1966). 
There is only one report of the photochemical syn-
1 Quantum yield is denoted by the symbol cfi, and is 
defined as the number of species undergoing a process 
per number of quanta absorbed. 
10 
thesis of HCN from CH4 - N~ mixtures (Dodonova, 1966). 
The author detected the formation of HCN in very low 
yield (20 nmoles) after irradiating (125- 170 nm) for 10 
hours a one to one mixture of CH4 - N~ at 5 - 8 Torr. The 
mechanism of formation was not studied but it was 
suggested that photoactivated Nz and its interaction 
with ?CH: radicals could account for its formation 
(Dodonova, 1966) . Chang et al. (1979) repeated this 
experiment using a monochromatic hydrogen lamp emitting 
at 123.6 nm. HCN or other N- containing organics were 
not d etected. Experiments performed at higher wave-
lcncths did not produce any detectable amount of N-
containing organic compounds (Bossard et al., 1981). 
Contrary to the unsuccessful efforts of Chang et 
al . (1979) to duplicate the experiments of Dodonova 
(1966) , the formation of HCN from the reaction of Cfk: 
radicals with N2 has been demonstrated by Laufer and 
Bass (1978) . These authors studied the kinetics of the 
reac tion (1.8) using flash photolysis on CEkCO- Nz and 
CEkN2-N2 gas mixtures, and determined that its rate of 
reaction is small (~6X10'4 dm-3 mole- 1 s- 1 ). 
CEk: + Nz HCN + :NH ( 1. 8) 
Another possible channel for the formation of HCN 
11 
is the reaction of ?CH: radicals with N2 . Braun et al. 
(1967) have presented kinetic evidence for the reaction 
(1.9) using flash photolysis (136 nm) on Cf-lq_-~ mix-
tures . The rate constant was estimated to be 4.3X107 
dm3 mo l e- 1 s - 1 , but the products were not identified 
(Braun et al., 1967). 
? CH : -+ ~ products ( 1. 9) 
Ultraviolet light was an abundant source of energy 
in the primitive Earth . A total flux of 0.32 kJ cm- 2 
y- 1 of UV light (wavelengths ~200 nm) enters into the 
upper Earth's atmosphere at the present time (Fox and 
Dose, 1977). Astronomical obs ervations suggest that 
the early Sun emitted 10- 1,000 times its present value 
in the spectrum between 100 and 200 nm (Canuto et al., 
1982). However, despite the possible great abundance 
of ultraviolet light, it seems likely that photoprcxiuc-
tion of HCN in the primitive Earth was not efficient 
(Raulin et al., 1982) . 
1.2.2 Radiolysis 
Irradiation of N2 leads to its dissociation, reac-
tion 1.10 (Harteck and Dondes, 1957, 1958a,b). The ef-
12 
fec t s of ionizing radiation on methane has been 
extensively studied, and this system is reasonably well 
understood (Lind and Bardwell, 1926; Hoing and Shep-
p ard , 1946 ; Lampe , 1957; Maurin, 1962; Hauser, 1964; 
Rebbert and Aus loss, 1973; Arai et al . , 1981a,b) . The 
mechan i sm of d ecomposition of methane involves ionic 
and rad i cal processes . The principal ion formed at 
a t mos phe ric pressure is Cfb -+- (Fie ld et al., 1963); its 
o r i g i n and fate during radiolysis are (Maurin, 1962) : 
I rradiat ion 
Nz - N : + . N : ( 1. 10) 
c~- + e (1.11a) 
Irradiation 
CH.q I : c~- (1.11b) 
CH" - CH3 ? + H? ( 1. 12) 
CH.q-+- + c~ CEb + + CH3? ( 1. 13) 
Clb+ + c~ (kfb -+- (1.14) 
The major products from the radiolysis of methane 
are Ek, GzH..,, CbHe, n - ~810 {Lind and Bardwell, 1926; 
Ho ing and Sheppard, 1946; Lampe, 1957; Maurin, 1962; 
Hauser, 1964; Rebbert and Ausloss, 1973; Arai et al., 
1981a, b). 
The radiochemical formation of HCN in a C~ - N:z 
13 
mix?ture has been studied by Zhdamirov et al. ( 1970). 
The auLhors studied the dependance of the radiation 
c h e mical yi elcF of HCN as a function of composition of 
mixture, tempe rature, pressure and dose rate. G (IICN) 
has a well - marked dependaace on the composition of 
ruixLur- e , r eachinr; iLs maximum valu e (G =-0. 9) at, 5 - 7% 
me Lb cn1 c cont,ent. Th e tempe rai.,ure depe nd a nce of G (HCN ) 
over i.,b e ranirc: 30 - 400 "C is not of th e usu a 1 Arrb en i u:. 
ty ? e ; i.,b e graph of locr G (HCN) vs 1/T ba s two parts, 
und th e energy of activations were estimated to b e 
2. 9 k,J mo l e -? 1 and 16. 2 k,T mole- 1 at low (30- 100?C) and 
high (200- 400?C ) temperature, respectively. G (HCN) 
can h e increased up to 5 . 9 at 400?C and aLmospheric 
pressure (Zhdamirov et al., 1970}. Although a 
mechHr1i s m was not proposed by the authors, the stronn 
depe ndarwe of G ( IICN) on dose rRte3 suggests that HCN 
is formed by radical - radical reactions. A like ly cban -
nel for its formaLion is: 
Cfh? + ?N: HCN + I-k (1.15) 
2 Radiation chemical yield is denote d by the symbol G , 
and is tbe number of molecules formed or destroyed per 
100 eV of energy absorbed. Th e equivalent of 1 G unit 
is 1 . 0364 X 10- 7 mole J - 1 . 
3 G(HCN) increases 4- 5 times by changing the dose rate 
from 1013 to 101 0 eV cm- 3 s - 1 (Zhdamirov et al., 1970). 
14 
Armstrong and Winkler (19 55 ) studied such a reaction, 
and determined that its rate coefficient is about 
Another source of HCN at low dose 
rates could b e the react ion of active nitrogen with CH4 
(reacti on 1.16). Froben (1974) detected the radical 
IL C=- N- from this reaction by e l ectron spin r esonance at 
77?K. 
CH.q + . N : fk C=N? + fk (1.16a) 
EkC=N? HCN + H? (1.16b) 
Solar wind and cosmic rays were probably the maJor 
sourcP.s of ionizing radiation on the top of the primi -
tive atmosphere Earth (Or6 et al., 1977); their 
abundances on the contemporary Earth are estimated to 
b e 0.84 J cm- 2 y- 1 and 0.0063 J cm- 2 y - 1 , respectively 
(Or6 et al . , 1977). A dose rate of 5X1010 eV cm- 3 y- 1 
can b e derived from these values. An estimate of 
radiochemical production of HCN in the upper parts of 
the primitive atmosphere would vary from 10- 0 to 10-4 
mo le dm- 3 y- 1 based on the fluctuation of G (HCN) 
determined under various experimental conditions (0 . 01 
to 0.9) by Zhdamirov et al. (1970). 
Ionizing radiations on the surface of the primi -
tive Earth originated mainly from the decay of radioac-
15 
tive isotopes such as 
1,;,K40. Estimates of their abundance 4 billion y ears 
ago depend on the model used . If we assume homo -
geneous distribution of these elements in the Earth 
crust, the energy produced per unit time projected per 
square centimeter of surface is 11.72 (Mil ler and 0r-
gel, 1974) or 196.65 J cm-2 y- 1 (Fox and Dose, 1977) 
for 1 or 10 km depth, respectively. A dose rate range 
from 7X1019 to 1X1<>2 1 eV cm- 3 y- 1 can be derived from 
these values for the atmosphere at the surface of the 
Eart-h . An estimate of radiochemical prcx.iuction of HCN 
would therefore vary from 10-e to 10- 1 mole dm- 3 y- 1 
bas e d on the fluctuation of G (HCN) determined under 
v~rious experimental conditions (0.01 to 0 . 9) by 
Zhdamirov et al. {1970) . 
1.2.3 Electrolysis 
The mechanism of decomposition of methane is not 
well understocxl {Bossard et al., 1982). The major 
hydrocarbons {Ponnamperuma and Woeller, 1964; Ponnam-
peruma and Pering, 1966; Ponnamperuma et al., 1969). 
Their relative yields depend on the pressure of the 
system and current of the electric discharge . At low 
16 
pressures ethane is the most abundant hydrocarbon (glow 
discharge ), but as the pressure is raised to atmos -
pheric levels, a c etylene becomes the principal product 
(spark d ischarge ) (Fujio, 1930; We iner and Bu r ton , 
1953 ; Sieck and Johnsen, 1963; Borisova and Eremin, 
1968) . At highe r currents ( s ilent and corona d is-
c harge s), ethan e is the most abundant hydrocarbon even 
at a~mosph e ri c pre ssures ( Li nd and G]ockl er , 1929 , 
1930; Lind and Schltze, 1931; Ponnamperuma and Woeller, 
1964; Ponnamperuma and Pering, 1966; Ponnamperuma et 
al . , 1969 ) . 
Th e fi rst report of electrosynthesis of HCN from a 
s imulated atmosphere of CH4 - Nz is that of Sanchez et 
al . ( 1966). Toupance et al. (1975) carried out a 
series of invest igations on the yield of formation of 
HCN as a function of N:z percentage in Cfk - N:z mixtures. 
They found that maximum production of HCN occurs in 
mixtures composed of 70% N:z and 30% Cfk (Toupance et 
al., 1975). Mo lecular hydrogen formed in situ (Raulin 
et al . , 1982) or added prior to electrolysis (Stribling 
and Mi lle r, 1987) decreases the rate of formation of 
HCN . 
Chemical yields (G) of products formed in electric 
d i scharge experiments are usually not reported because 
17 
of the difficulty in determining the energy introduced 
by electric discharges (Navarro-Gonzalez et al., 1986). 
In an attempt to measure the yields of HCN from CH4 - N2 
mixtures subjected to electric discharges, Stribling 
and Miller (1987) estimai.,ed the energy introduced by 
comparing the heai., evolved in the experiment with that. 
of a known power source. The ability to reproduce 
i.,beir measurements was d etermined to be within a facto r 
of i.,wo (Stribling and Mill er, 1987). However, the 
authors did not take into account the energy converted 
into chemical form, light or that not absorbed by the 
gas. Gases have a low collisional mass stopping power 
when they are irradiated with low energy electrons 
(Spinks and Woods, 1976), as in the case of electric 
discharges. Therefore, their method underestimates the 
amount of energy supplied by electric discharges . 
Electric discharges are generally considered to be 
very efficient in synthesizing HCN based on the initial 
amount, of CH.q converted into HCN (Miller and Orgel, 
1974; Raulin et al., 1982). However, further work 
needs to be done in order to understand the mechanism 
and efficiency of HCN synthesis induced by electric 
discharges in the primitive atmosphere . 
18 
1.2.4 Pyrolysis 
'!'he thermal decomposition of methane has been 
extensively studied under a variety of conditions 
(Skinner and Ruehrwein, 1959; Kevorkian et al . , 1960; 
Kozlov and Knorre, 1963; Palmer and Hirt, 1963; 
Kondratiev, 1965; Harting et al., 1971). The rate of 
decomposition of methane is independent of pressure , 
reac~ion conditions (flow, static, or shock wave pyro-
lysis), and presence of an inert gas; the energy of 
activation calculated under various conditions is about 
423 kJ mo le- 1 in the temperature range of 900-2,000?K 
(Skinner and Ruehrwein, 1959; Kevorkian et al., 1960; 
Kozlov and Knorre, 1963; Palmer and Hirt, 1963; 
Kondratiev, 1965; Harting et al., 1971; Chen et al . , 
197 5). 
The dissociation reaction leading to the decom -
position of methane is shown in reaction 1.17. 
Dimerization of CEh? or H? leads to the formation of 
the initial products: C2Ho or lb, respectively. 
Ethane is, however, rapidly consumed during the pyro-
lysis leading to the formation of ethylene, the 
The latter further reacts to 
secondary product. 
produce acetylene, the tertiary product, as the extent 
of the reaction is increased (Chen et al., 1975; Roscoe 
19 
and Thompson, 1985). 
Heat (1.17) 
CH.,. CH3 ? 
+ H? 
tmosphere 
The shock wave pyrolysis 
of a CH4-N:z a
s of 5% CH.,. 
was studied by Rao et al.
 (1967). Mix~ure
% N~ in argon were shock-
heated to temperatures 
and 5
ide is formed 
between 1500 and 6000?K. 
Hydrogen cyan ' 
 
tarting from 2500?K and i
ncreasin~ in yield up to
s
 
t 20% at 5000?K (Rao et a
l., 1967). The second
abou
r rate of formation for HCN
 was determined as 
orde
1 
1 n:r mole- s - 1. 
k (CH,, + N:z) = 9. 32X10-
3 - 5. 021 , in d
-
 mechanism of formation w
as not studied but a pos
The
ne 
ible scheme consistent wit
h the mechanism of metha
s
fol -
pyrolysis was suggested (
reactions 1.18 to 1.23, 
lowed by reactions 1.15 a
nd 1.16). 
( 1. 18) 
T22500?K N:z* 
N2 + H? ( 1. 19) 
CE-b: + N:z 
CH3 ? + N:z* 
+ N:z + H? 
(1. 20) 
? CH: 
CI--k: + N:z* ( 1. 21) 
? CHN2* 
? CH: + N:z* ( 1. 22) 
2 HCN 
? CHN:z* + ? CH: ( 1. 23) 
+ . N: HCN 
? CHN:z* 
20 
The chemical yield calculated for HCN was G 3.2 
(Bar -Nun and Shaviv, 1975). Thi s value is high 
compared to that obtained by radiolysis (section 1.2 .3) 
and makes shock waves the most efficient energy source 
for producing HCN under thes e conditions. Bar- Nun and 
Taul>cr ( 1972) hav P- estimated thnt shock waves in the 
primitive atmosphere we re efficiently produced by 
lightine and met,eoritic impact, and an al>undance of 
4.18 J cm- 2 y - 1 has Leen estimated. A d ose rate of 
2.6X1019 eV cm- 3 y - 1 can be derived from this value. 
An estimate of the shock wav e production of HCN in the 
primitiv e atmosphere is lCJ" 2 mo l e dm- 3 y- 1 taking into 
a c count a of G=3.2 for HCN. 
1.3 Distribution of HCN 
HCN is ubiqu i tous in nature. It has b een detected 
in the interstellar me dium {Snyder and Buhl, 1971), 
comets (Ulich and Conklin, 1974), and in the atmos -
pheres of Jupiter {Tokunaga et al., 1981), and Titan 
{Hanel et al . , 1981, and Owen, 1982). Small amounts of 
HCN occur on the contemporary Earth; this is bio-
synthesized from amino acids by several photosynthetic 
and non - photosynthetic bacteria (Nazly et al., 1981), 
algae {Vennesland et al., 1981), plants (Nartey, 1981), 
21 
and arthropods (Duffey, 1981). 
The probaLl e o c curre nce of HCN ou the primitive 
Earth is supported by its facile formation under a 
vari e ty of conditions . Table 1.1 summarizes the 
est ima t e d productions of HCN in the primitive atmos -
ph c~ r e indueed by different energy sources. 
Table 1. 1. Estimated productions of HCN in the primi --
t i v e atmosphere by diffeninL energy sources . 
Energy source G 0 (HCN) HCN production 
(mole dm- 3 y- 1 ) 
UV light negligible 1 negligible 
Ionizing radiation: 0.01-0.97 
Upper atmosphere 10- b - 10- .q 
Lowe r atmosphere 10- 5 - 10- 1 
Electric Discharges undetermined 
Shoc k waves 3. 23 
Total 
1. Raulin et al., 1982; 2. Zhdamirov et al., 1970; 
3. Bar- Nun and Shaviv, 1975. 
HCN synthesized in the primitive atmosphere would 
22 
h a ve been effici e ntly transported into the oceans by 
p reci pitation processes wh e re abiotic syntheses of 
compl e x organi c mo l ecul es may occur (Oro and KimLa ll, 
196 1 ) . Fee ly et al. (1986} have d e rive d a HCN rainout 
r a Le of (3 - 14)X1011 mo le y 1 taking into account a 
He nry ' s law constant of 4Xl03 , a IJCN gloLa l mixing 
ra t io of 10- 6 , and a globa lly rainfall r a t e of 3.3X1(~ 6 
It is difficult to estimate the concentration of 
HCN or any other compound in the primitive oceans. 
Miller and 0rgel (1974} have attempted to estimate the 
p oss ible uppe r limit of organic compounds dissolved in 
t h e prim i tive hydrosphere. They rationalized that jt 
i s v e ry unlikely that all of the surface carbon was 
eve r present as organic compounds, but 1 to 20% might 
have been. If the volume of the primitive oceans was 
as large as the present ones, this would have given a 
solution of 0.01 to 0 . 10 mole dm- 3 for a one- carbon-
atom organic compound such as HCN (modified after 
Mi ller and 0rgel, 1974). This approximation places 
only an upper limit since not included in the calcula-
tion is the loss of HCN by polymerization and/or hydro-
lysis in the oceans. Such a high steady- state concen-
tration does not seem likely since hydrolysis to formic 
a c id r e quires at most a short period of time ( 1()3 to 
---- -
23 
104 years) at moderate pH and temperature (Sanchez et 
al., 1966). 
The simplest mechanism that might have operate d on 
Ui e primitive Earth for concentrating organic compounds 
is evaporation {Miller and Orge l, 1974). Such a 
mechanism is unlikely to have contributed for the ac-
cumulation of a volatile compound such as HCN. Sanchez 
et al. {1966) have suggested the eutectic freezing of 
HCN - water mixtures as a possible mechanism to increase 
the concentration of HCN. The eutectic in a HCN- water 
system occurs at -23.4?C and contains 74 . 5% w of HCN 
{Sanchez et al., 1966). This mechanism possibly 
ope rated on confined areas on the Earth such as polar 
regions, but was not dominant on a global perspective 
for the Earth since many of the physical conditions 
that prevailed in the early Earth were probably not 
significantly different from those that exist today 
(Ferris and Hagan, 1984); in particular, oceans and 
other bodies of water were subject to similar buffering 
processes, resulting in a pH that presumably was close 
to that of modern oceans (pH 8.0-8.5), or at least not 
far from neutrality (Ferris and Hagan, 1984). 
Navarro-Gonzalez (1983) has suggested the forma-
tion of cyanocomplexes as a mechanism to protect HCN 
24 
from hydrolysis and to accumulate it in a nonvolatil e 
?arm. Cyanocomplexes are readily formed when a cyanide 
s o lut,jon is in cont-act with rocks. Beck {1978) has 
shown tb aL when 1 R of powdered rock is suspended in 10 
ml of 0.014 mo ] e d~ 3 aqueous solution of KCN, a 
varieLy of cyanocom11]exes of transition elements suc h 
ai; Mn , Fe, Co, Cu, and Mo are form ed . Equilibrium 
conditions are reac h ed within 36 hr, and the steady 
:::: t, a t e concentration of cyano complexe s varies from 10- 5 
to 10- 4 mol e dm- 3 depending on the type of roc k; bexa-
cyanoferrate ( II) and/or (III) were in most cases the 
principa l cyanocomp]ex formed (Beck, 1978). 
Kobayashi and Ponnamperuma (1985b) found that the 
yic Jd of HCN in the electric discharge of C[l<i - N2-t:bO 
mixtures could be increased over 200 times if metal 
jons such as Fe2-. Zn2 -, and Moo... 2 - were included 1n 
the liquid phase. They proposed the formation of 
cyanocomp]exes in the liquid phase as a mechanism to 
protect, HCN during electrolysis. 
Formation of cyanocomplexes of transition metals 
in the primitive ocean could have been an important 
mechanism to protect HCN from hydrolysis and to allow 
its accumulation over extended periods of time. In the 
absence of such a process, hydrolysis of HCN would 
25 
require a short period of time (1<>3 to 104
 years) at 
moderate pH and temperature (Sanchez et al
., 1966 )_ 
The source of transition metals for the pr
imordial 
hydrosphere was the lithosphere (Beck, 197
8). Among 
the different transition elements present 
in the 
lithosphere and hydrosphere iron is by far 
the most 
abundant (Weast et al., 1985). The concentrati
on of 
ely 
iron in the contemporary hydrosphere is ex
trem
small, e.g., 3.5X10-
0 mole dm- 3 for sea water (Brewer, 
1975) and l.2Xl0-0 mole dm-
3 for river water 
l concentration 1S a 
(Mackenzie, 1975). This sma
l
consequence of the low solubility of iron(
III) 
and the absence of complex- forming ligands.
 
hydroxide, 
During the early stages of the primitive h
ydrosphere, 
iron was probably present in its more solu
ble form, 
iron(II). Hydrogen cyanide may have played
 an 
important role in increasing the dissolutio
n of iron 
and other metal ions from the lithosphere 
(Navarro-
onzlez et al., 1989). Cyanocomplexes of ir
on are 
G
4 
characterized by their high solubilities
in water, and 
ole dm-3 
4 Maximum solubility varies from 0.06 to 0.22
 m
for potassium or sodium bexacyanoferrate(I
I) at 0 and 
l00C, respectively (Weast, et al., 1985). 
26 
h i gh s t ability constantse . 
1.4 Formation of biomolecules from BCN 
I t is gene rally accepted that HCN synthesized in 
the prim i tive atmosphere would have bee n efficiently 
trans porte d into the oceans where it played a signifi -
can t r o l e in the process that preceded the emergence 
o f life {Ore and Kimball, 1961; Sanchez et al . , 1966; 
Ferris and Hagan, 1984). A number of studies has been 
devoted not only to the identification of prcx:lucts 
r esulting from the oligomerization of HCN but also to 
t he elucidation of the mechanisms for their formation . 
This sect ion reviews the current status o f the studies 
of the ol i g omerization of HCN in aqueous solution 
initiated by ionic (section 1.4.1) or radical processes 
(section 1 . 4 . 2) . It also examines two possibly 
c ompeting processes in the primitive oceans: 
Hydrolysis vs oligomerization of HCN (section 1.4.3) . 
e The stability constant varies from 2.5Xl<P~ to 
4 . 0X 104 3 for hexacyanoferrate(II) and (III), respec-
t i vely (Smith and Martell, 1976). 
27 
1.4.1 Ionic oligomerization 
It h as b een kn own since the last century that HCN 
joni c nlly o}j[!omerizes in h asic mt-:dium giving ri se to a 
variety of oligomers, generically rei"erred as "azulmic 
Hc ids " (Volker, 1957, 1960; S~haefer, 1970). Diamino -
mHleonjtrile (DAMN), a tetramer of HCN, is the smallest 
uligumer isolable from an oligomerizing 0. 1- 1 . 0 mole 
dm- 3 aqueous HCN solution at room temperature {Sanchez 
et al . , 1967). The initial steps leadinCT to th e forma -
tion o f DAMN are shown in Figure 1.1. Th e postulated 
~ Lf!?wi se condensation of HCN to form DAMN is suppor-t,ed 
by the obse rvation of forma tion of maleonitrile deriva-
tives from N- alkyiminoacetonitriles in aqueous HCN 
2 HCN HN =CHCN < I r:l N) 
f I[ N -i HN=CHCN <AHN) 
HCN + (ORMN) 
Figure 1 . 1. Formation of DAMN : Initial Steps in the 
ionic oligomerization of HCN. 
28 
solutions (Ferris et al., 1972); no dimerization of 
the substituted iminoacetonitriles was observed (Ferris 
et al., 1972): The suggestion by Kliss and Matthews 
{196 2 ) that the HCN dimer is a direct precursor to DAMN 
m1<l l a r g er oligome rs therefore does not appear viuble 
{Ferr i s et al., 1972). 
Conside rably progress has been mad 8 in the charac-
t e rization of some of the products from the ionic 
oligoroerization of HCN (Ferris and Hagan, 1984). A 
s umma ry of the data is given below. 
HCN_dime r. Some controversy has arisen in the 
literature over the proposed structures of the dimer 
{Kli ss and Matthews, 1962; Loew and Chang, 1971; Loew, 
1971; Moffat, 1975; Yang et al., 1976). Since its 
steady state concentration in an oligomerizing cyanide 
solution is very low (Ferris and Hagan, 1984), it has 
never been detected or isolated from solution. A di -
radical structure, aminocyanocarbene, was suggested 
(Kliss and Matthews, 1962), but there was never any 
direct evidence for such species. On the contrary, 
several different sets of quantum mechanical calcula-
tions have shown that iminoacetonitrile (IAN) is the 
most stable conformation of the dimer (Loew and Chang, 
1971; Loew, 1971). Another dimer of HCN, azacyclo-
29 
propenylidene, was also proposed as a stable form based 
on IND0 calculations (Yang et al., 1976), but Moffat 
(1975) pointed out that such a calculation overes -
timates the stability of the three- member ring. 
Aminomaleonitrile (AMN), the trimer of HCN, is 
also present in such a low steady state concentration 
that it has not yet been isolated from an oligomerizing 
cyanide solution (Sanchez et al., 1967). AMN can be 
synthesized and stored as the tosylate salt (Ferris et 
al., 1973). AMN reacts rapidly with HCN to form DAMN; 
its half-life is of the order 102 sin a 1.0 mole dm- 3 
HCN at 25?C and pH 9.2 (Sanchez et al., 1967). 
DAMN is formed essentially irreversibly as shown 
by the lack of exchange of 13 C-labelled HCN with DAMN 
(Ferris and Edelson, 1978). Spectroscopic evidence 
suggests that the cis conformation is formed (Long et 
al., 1960). Tetramerization of HCN occurs in the pH 
range 8.5-10.0, reaching a maximum at pH 9.2, which is 
the pKa of HCN (Sanchez et al., 1967). The tetra-
merization kinetics have been studied by Sanchez et al. 
(1967) and Toupance et al. (1970); and a rate 
expression, 
k(HCN + - cN)=ko exp( - EA R- 1 1 1 ). 
30 
wa s derived wh ere, k.-. =5.1X107 dm'"" mole- 1 s- 1 ; and 
&:. = (81. 6?2.1) kJ mole- 1 (Toupance et al., 1970). 
Diiminosuccinonitrile, DI SN, is formed by oxida -
Lion of DAMN (Ferris and Ryan, 1973; Ferris et al ., 
198 1a , 1982). Reaction 1.24, unbalanced, exemplifies 
its formaLion; the oxidizing agent invo]ved durinP," the 
oligome rization of anoxygeni c aqueous solutions of HCN 
has not yet b een identified (Ferris and Ry an , 1973). 
~IN_~~r _,,C N HN~CN 
J~
N ~ ( 1. 24) H~''CN e' <-~H 
D(:JMN DJ SN 
DISN i s a r eactive species that unde r goes hydro-
lysi s to yield oxalic acid and HCN (Ferries et al., 
1982), and ammonolysis to yield urea and oxalic a cid 
(Ferris and Ryan, 1973) . 
~denin~. a pentamer of HCN, was detected by Or6 
( J 960), Or6 and Kimball ( 1961), and Lowe et al . ( 1963) 
when 1.5- 3.0 mo le dm- 3 ammoniacal solutions of HCN were 
h eated from one to several days at temperatures ranging 
from 27 to 100?C. Ferris et al . (1978) working under 
mild er conditions found that adenine could be detected 
31 
only afLe r acid hydrolysis of the solution, a 0.1 mole 
drn --:~ Nfl"'CN aqu eou!:_~ solut,ion at, pII 9.2, k e pt at 25?C for 
4 - 12 months . Thi s observation suggests that ad enine is 
form e d as a sub~~t.i tut,ed derivativ e or is chemically 
associated with higher BCN oligomers (Ferris et a l., 
1970). Several me c h anisms h a ve b een proposed for its 
formation (Ord 196 1; Kli ss and Matthews, 1962; Sanchez 
et al . , 1967; l<'erris et al., 1978); howe ver, Voet, and 
Schwa rtz (1983 ) h a v e recently isolated and identified 
adeni n e - 8 - carboxamide, (adenine - 8 - CA), in an oli~o-
me rizine HCN solution. This purine derivative releases 
ndcnine upon hydrolysis. Based on thi s finding, Voe t 
and Schwartz (1983) have proposed an original mechanism 
for t,he formc:1t, ion of ade nine ( Figure 1. 2 } . Support in[; 
evidence for such a mechan ism was based on the isola -
tjon Find id e ntification of three different imidazole 
derivatives presuma bly involved in the r e action 
mechard sm ( Voet, and Schwartz, 1983). 
fl jgh e r HCN oligomer~. The structure and mechanism 
of formation of higher oligomers is much less clear. 
Subsequent oligomerization steps appear to involve a 
series of internal redox reactions, inferred from the 
detection of oxidation products (oxalic and urea) as 
we ll as reduction product,s (2,3 - diaminosuccinic acid) 
in the oligomer hydrolysate (Ferris and Hagan, 1984). 
32 
NH 
NC,,r('N H2 -RH Nc)\-;-N 
)l_ + JL_ ')-rn 
NC- ' N H2 H N' N- H 
2 
J HCN 
NII;, N~' xNH:, ) , N H2 0 N~- -,, ') ~H H2 0 NH1 7 ~ I , ~( I ;N :-cN ~ ~----N- H i~ N- H 0 
CDC I NH3 
Rdenine Rd en ine - 8- CR 
Fi~ure 1 . 2 . Mechanism of Adenine Synthesis according 
to Voet and Schwartz (19 8 3) . 
It was suggested that DAMN- DISN interconversion could 
b e mediating these processes (Ferris and Ryan, 1973) . 
The elucidation of the structure of HCN oligomers 
1s comp licated by the he~erogenous nature of the 
material, and only limited progress has been made in 
this area. Partial characterization of the solubl e 
fraction by 1 3 C- NMR, and differential thermal analysi s 
indicated the presence of carboxamide, -X-C(=O)-NEk, 
and ure a groupings, -X-NH-C(=O)-NH- X- (Ferris et al . , 
1981b). Pyrolysis of HCN oligomers at 600?C resulted 
33 
in the release of gaseous products such as HCN, CO:z, 
CEbCN, HCONfk, and pyridine. The pyrolytic formation 
of these products is consistent with the presence of 
carboxylic and amide groups in HCN oligomers. Hetero-
c yclic ring systems and structures which are thermal -
ized to heterocycles are indicated by the formation of 
pyridine and HCN (Ferris et al., 1981b). 
At present it is clear that higher oligomers of 
HCN contain a more complex variety of functional units. 
This complexity is apparent in the diverse mixture of 
products that have been identified upon hydrolysis of 
the oligomers such as : 
a . Amino acids: alanine, /::-alanine, u -
aminoisobutyric, aspartic, a, 13-diaminopro-
p1on1c, and diaminosuccinic acids, glycine, 
glutamic, and guanidine acetic acids, 
isoleucine, leucine, and serine (Oro and 
Kamat, 1961; Lowe et al., 1963; Ferris et 
al., 1978); 
b. Purines: adenine, and hypoxanthine (Lowe et 
al., 1963; Ponnamperuma, 1965; Ferris et 
al., 1978); 
c. hrimidines: 4,5- dihydroxypyrimidine, 5 -
34 
hydroxyuracil, uracil, and orotic acid (Fer-
ris and Joshi, 1978; Ferris et al., 1978; 
Voet and Schwartz, 1982); 
d. flydantoins: hydantoin, 5,5-dimethylhydantoin 
and 5- carboxymethylidine hydantoin (Ferris 
et al., 1974b); 
d. Urea (Lowe et al . , 1963; Ponnamperuma, 
1965). 
1.4.2 Free-radical oligomerization 
The free - radical oligomerization of HCN in aqueous 
solution has been mainly studied using ionizing radia-
tion as a source of free radicals (Draganic and Dra-
ganic, 1977). The interaction of ionizing radiation 
with liquid water and dilute aqueous solutions is one 
of the best understood domains of radiation chemistry 
(Spinks and Woods, 1976). The generally accepted 
scheme of water radiolysis is summarized by reaction 
1 . 25 (Draganic and Draganic, 1971). In pure water 
there is scarcely any net decomposition because the 
radiolytic products undergo very efficient back reac-
tions leading to the re-formation of water (Buxton et 
al., 1988). 
35 
Radiation 
IkO ( 1. 25) 
The radiation chemical yields {G) for this process 
are G ( - I-k0) =4.1, G (e..q- ) =2.65, G (H? ) =0 . 55, 
0 {HO? ) =2. 74. G (I-b ) =O. 45, G {lkOz )=O. 68, and 
G (I-l-+- ) =2.65 (Draganic and Draganic, 1971; Buxton et 
al ., 1988). 
When dilute aqueous solutions are irradiated prac-
tical ly all the energy absorbed is deposited in the 
wate r molecules and the observed chemical changes are 
brought about indirectly via the molecular products 
{fkOz ) and, particularly, the radical products (H?. HO-
and e.q- ). Direct action due to energy deposited 
directly in the solute is generally unimportant in 
dilute aqueous solutions, i.e., at solute concentra-
tions below about 1 mole dm- 3 (Spinks and Woods, 1976). 
Other sources of these radicals in liquid water 
are photolysis at s 200 nm,~ (H?, ?OH) =0.36; 
~ = (e.q- }~0.04 (Bamford and Wayne, 1967, Harting and 
Getoff, 1980), sonolysis (Weissler, 1953, Tain- Jen et 
al .? 1980), and electrolysis (Terasawa and Harada, 
1980, Harada et al ., 1984). 
3 6 
AL presen t, it i s diffi c ult to e s timate the r ate of 
production of H? , HO?, and e.q - in the prim i tive h ydro-
s ph e re , ; h owe v e r, b as e d o n th e abundance o f ul-Lravi o l et 
] -ie-ht, , r adioact i vity and lightning on th e pr i mi tive 
l:!:hrLl1, it i s lik e l y -that these r eacLive s p ec ies c on-
trihut,ed signifi cant,ly to free- rad iea l r C:: a e ti o n s of 
nb :iut, jr ? si[!nif ican ce in the primitive hyd r osphe r e 
( Ni k f : Li c, 1 9 8 4 a ) . 
Tho r eacL ion of H? with HCN h as b een studied b y 
Onura (1 968 ) and Dragani c et al. (1 9 7 3 ) u s in[f comp e-
ti tion k i n et i cs i n ,: - irradiate d aqu e ous ~~( i] u ?Lions. Th e 
raLc con s Lan t was d e t e rmin e d t o b e: 3 . 3Xl07 d m3 mo l e - 1 
s - 1 The r ad i ca l( s ) p rodu ced in this r e a c ti o n (1.26) 
ha v e b een ide nti f i e d by e lectron spin r esonance in 
cry st,al matri ces (Coebran et al., 1962 ) and in aqu e ou s 
so lutions ( Ne ta and Fessenden, 1970; Be h a r and Fess e n --
d c n, 1~172 ), and also by fast spec troscopi c t echniques 
u s i n ~ pul sR radi o lysi s in aqu e ous solutions (Buchler et 
al., 1976; Drag anic et al . , 1976b). 
HCN + H? fkC =N? ( 1. 26) 
At pH greater than the pKa for HCN (9.2), cyanide 
1 on r eact s with H? (reaction 1. 27): 
37 
- cN + H? l-b C=N? { 1. 27) 
Anbar a nd Ne ta (19 6 7) have reported that the rate o f 
this r e a c tion is 2.6X1if' dm3 mo l e- 1 s - 1 ; h owe ver, the 
cond i tions used to obtained the rate constant are 
poor l y d e fin e d (Anbar and Ne ta, 1967) and the pH (7) 
u sed to me asure the parame ter is smaller than the pKa 
fo r HCN; a s a consequence the concentration of cyanide 
was n egligible . This value should there fore be use d 
wi t,b cau ti on . 
The reaction (1 . 28) of e.q- with HCN has also been 
studied by Ogura (1968) and Draganic et al. (1973) 
u sin g competition kinetics in \:.' - irradiated aqueous 
solutions. The rate constants determined by the dif-
fe r e nt authors are 2. OX1CJ3 and 6 . 6X1CJ3 dni'5' mole- 1 s - 1 , 
respectively. The latter value may be considered more 
r e liable since it was obtained at lower doses where the 
reaction mechanism was not complicated by secondary 
reactions. The same radical(s) is (are) produced as 
for H? {Draganic et al., 1973). The reaction of 
cyanide with e.q- is negligible, k~1()6 dm3 mole- 1 s - 1 
(Anbar and Hart, 1965; Bielski and Allen, 1977). 
38 
IL,() 
HCN c .. ,, f l ('N? + no-- ( 1. 28) 
Dragan:i c et al. ( U/'/ '.l) determirwd tbe upper limit 
(k <&XJO" drn ? mu l e 1 ~; ') lrll:? the rat,F> of rea c tion 
( 1. 29) or llU? wj Lh HCN w :i nr; com?e ?Ljtion kine ?Lics 1n 
i r-rHd j H Led solu L j on:?: 
flCN -1 110? (1 . 29) 
1 
mq)1 1 :..; ' for r-Pac :Lion 1. 2~' using pulse radiolysis 
coup 1 e el tu fast, k inr~L i r.::; i; p r?c troscopy, and optimizing 
Tb c struc i, ure o f UH ' radi cal produced by this reaction 
wa: ; j nfcrrcd from i -t1(' s Lull I I products ( Drc:1Ganic et a 1 . , 
1873) and also from specLro:;copy (Buchler et al., 197G; 
Several studies haVf ' lH!en don e t ,o determine the 
n1te of reaction (1. 30 ) o f 110? with - cN usine steady-
state radiolysis (Kralji c and Trumbore, 1965) and pulse 
r11<liolysis (Behar, 1 97 4 ; Bu ('hler et al., 1976; Bie]ski 
and Allen, 1977). Th e average value obtained from 
the different studies is 6 . !iXl09 drrr mole- 1 s - 1 ? The 
radical produced hav e b een detected by fast spectres -
39 
COJ'Y (Be h a r , 1974; Buchler et al., 1976). 
- CN + ?IO? H0 - C=N- ( 1. 30) 
~t, pll >11 the hydroxyl radical dissociates 
(pK- 11 . 9) producincr tbe hydroxyl radical anion (?O- ) 
(Dragan i c and Drag ani c , 1971). This radica] readily 
r eact s witb cyanide ion (reac tion 1.31), k =2.6X10'3 dm~ 
mo ] e- 1 s - 1 : 
- CN -1 ? o- (1.31) 
Tb ,1 trans i e nt radical produced by this reaction has 
h P-en dFd,ected :in pulse radiolysis studies coupled to 
fa s t spectros c opy (Behar, 1974; Buchler et al., 1976). 
The short- lived intermediates produced in reac-
tion ~ 1 . 26 t u 1.31 react among themselves and/or with 
HCN/CN- leading to the decomposition of HCN and to the 
formation of a large variety of compounds. Table 1.2 
summarizes the initial radiation chemical yields (GD} 
01 decomposition of HCN at various pH's. GD ( -HCN) is 
maximum at pH 6 (Draganic and Draganic, 1980). The 
variation of GD ( - HCN) with pH is primarily due to the 
40 
Tah l e 1.2. Init i al Radiation Chemical Yields (G 0 ) of 
Decomposi t,ion of HCN and - cN at d i ff e r ent pH 1 ? 
Compound pil Go 
HCN 2.4 5 . 8 
6 . 0 13.8 
NH..qCN 9.2 6 .5 
NaCN (or KCN) 11. 3 5.2 
1. Draganic and Draganic, 1980. 
diffe r e nces of rates of reactions of H?, HO?, and e-. q 
Cons iderable progress has been made in the 
charact,erization of some of the stable products 
produced in the free- radical oligomerization of dilut,e0 
aque ous solutions of HCN (Draganic and Draganic, 1980) . 
About 79% of the nitrogen and carbon atoms from HCN 
mo l ecules decomposed are built into larger molecules, 
mainly various oligomers. A summary of the products 
that have been characterized is given below . Section 
1.4 . 2.1 examines the mechanism of formation and 
0 Unless otherwise stated, the data given is for 0.1 
mole dm- 3 HCN aqueous solutions. 
41 
chemical y ie l ds 7 (G) of low mo l ecular weigh t, p roduct,s 
wh:i le t;ect, i on 1. 4. 2. 2 d eals wi tb large r mol ecul es 
and / or small mo l eL:ule~~ released upon thei r hyd r olysis. 
1.4.2.1 Formation of low molecular weight prcxiucts 
in d ecomposi t ion of wa t e r mo l ecules {reaclion 1 . 25). 
Hydro1,;cn, G 0 =0. 4, a ccumulat,es dur i n ~ irradiation of t,be 
Fl CN so lution ( Draf; a ni c et al., 1973 ) . Hydroge n 
p e roxide , G 0 =0.3 for 0.006 mol e dm- 3 HCN, d isappe ars 1n 
re,H""! i , i ons wiU1 rad i olyt,i c produc t, s (Drartm1ic et al., 
19'/3; Ogu n~, 1968 ) . 
.C.11r b cln_ d i92(:jdE;., G 0 =0.8, JS formed with a 
signi ficant yield, but G rapidly dec reases wiU1 dos e in 
the kGy? ranee to about, 0 . 5. It,s mechani s m o f forma -
tion i s shown by reactions 1.32 and 1.33 . 
7 Unl ess olb erwi se stat,ed, the chemical yi e lds are the 
initial value s (G 0 ): Those determined at the lowes t 
pos s ible doses. 
0 Gray, Gy, i s the commonly used unit for radiation dose 
and its equivalent in SI units is l.8X10- 7 J mole- 1 ? 
42 
2Il0- CH -= N? llC( =NU)OH + HO- CN ( 1. 32) 
HO- CN + H20 C~ + NH~ ( 1. 33) 
Carbon dioxide accurnulat..es in solution due to its 
bir;h soluhi li ?Ly, and then re1,:H.:ts w.i.Lh hydrated 
e l ecL rons a s it., is indicated by r eaction 1.34 
(Drat~m1ic et al ., 1973; Dragani c and Drar;anic, 1980 ) . 
C<b -+ e-q . c<b- ( 1. 34) 
6Jn!!!Qlli.Q, G 0 =2.6, is formed with a higb yi eld , and 
it..s formati on may be explained by reactions 1.33 and 
1.35 to 1.37 (Draganjc et al., 1973). 
2 lbC=N? HCN + I-b C=Nll ( 1. 3~) 
fhC=Nll -+ l-bO HCHO + Nlh ( 1. 36) 
HC(OH)=NH + fh.0 HClliH + Nlh ( 1. 37) 
The amrnorna from ammonium cyanide or that produced 
radiolytically in cyanides is very reactive towards 
hydroxyl radicals (reaction 1.38), and the radical 
produced reacts with other intermediates or with solute 
producing the final products (Draganic et al., 1980) . 
Nib . + HO? Nib? + l-bO ( 1. 38) 
4 3 
8]d~l:LYde~ anrj ketones. The most abundant compou nd 
formcd is f ormnlclehycle, G 0 =- 1 .8, but G rap i dly d ecreases 
with :incre<:lsjnCT dose:: ( down to 0 .1} ( Oguri:i, 1960; 
DrR(';,rnic et a l., 1973}. I ts ori ft in cou ld b e explained 
hy r eac Lions 1. 3!:> a nd 1. 3G. At h igh d oses o f irrad i a -
tion, CH-. CllO, CII-. COCHO, and Cl:-b ( C0h-Clb are f ormed, anrl 
could o rig inate by short-ch a in olir:o rn eri:,:;at ion of the 
rad j c1-1 l ~~ produced by r eac-L ions 1. 2G t ,o 1 . ~i l ( Nc\v ar r o -
Gonz~] e z , 1983}. 
Carh_gx~]_i~ Ac~-!Q!J ~ Fo rm ic ac i d, G 0 -=- 0. 1 f o r 0. ()()(") 
mo l e d m?- 3 HCN, may b e forme d by rea c t.ion;-; 1. 34 and J . 37 
A large numbe r o f mon o - , di - , and tri -
Crir boxyli c a c id s we r e identified in HCN (pH=6) and 
NB-,CN ( p f1 =9. 2) : a c onitic, adipic, 1,2,4- butene- tricar-
boxy li c, butyri c , carboxysucc inic , citric, c itraconic, 
1,2- dime thyl - succ ini c , fumaric, glutaric, itaconic, 
mal c ic , mal i c, ma lonic, me thyl - maloni c , 2 - methyl - tri -
ca rl m llyli c, oxalie, pime lic, succinic, and tricarbal -
lyl ic (N a varro - Gonzal ez , 1983; Negron - Me ndoza et al., 
1 982, J 983 ) . Isolated, short- chain oligomerization 
mi ght, explain th e f o rmation of carboxylic acids or 
thei r amide s (Negr6n- Me ndoza et al . , 1983). 
Qre~ is an important product in the aque ous solu-
tion s of a mmon i um c yanide , pH 9.2, (G =0 . 65, 180 kGy), 
44 
but is formed in low yield in aqueous solutions o f 
hydrogen cyanide, pH 6 (G =0.03, 130kGy). It may b e 
formed by reactions 1.39 to 1.42 (Dragani c and 
Draganic, 1980; Niketic et al., 1983). 
? C ( OH ) =N- + fb 0 OH- + ? C (OH) =NH ( 1. 39) 
? C(OH)=NH NfkC=O ( 1. 40) 
Nfk C=O ? Nfb ? NfkC( =O)Nf-k ( 1. 41) 
HO - CN + NH3 Nf-k C ( =O ) Nfb ( 1. 42) 
Carbamyl glycinamide, IbNC(=O)NHCfbC( =O)NEk, is 
formed in low yield in HCN at pH=6 (G =0 . 02, 130 KGy). 
It has not yet been detected in NfkCN solutions, pH 
9.2. Carbamyl glycinonitrile, H:zNC( =O)NHCE-kCN, forms 
in low yield (G =0.05) in HCN solutions, pH 6 (130 KGy) 
and NI:-kCN solutions, pH 9.2 (180 KGy). These prcxlucts 
could originate by short- chain oligomerization of the 
radicals prcxluced by reactions 1.26 to 1.30, 1.38 and 
1 . 42 (Niketic et al., 1983). 
Amino acids. Trace amounts of amino acids were 
found in some cases of irradiated solutions. Their 
origin was attributed to partial hydrolytic breakdown 
of oligomeric material (Draganic et al., 1976a). 
~ - ---------------------------
45 
Heteroc clic com ounds. A large number of 
products is formed; however, the identification of most 
of them still remains to be done. They represent 2 - 5% 
of the total mass o:f all non- volatile products. 
Adenine, uracil, thymine, and cytosine are formed. 
There is evidence of the presence of triazines, but 
the y have not yet been identified (Ponnamperuma, 1965; 
Negron - Mendoza and Draganic, 1984). 
Heterocyclic products are most likely fragments of 
short, side- chains of ol igomers which are formed as a 
resu lt of free radical processes {Negron- Mendoza and 
Dragan ic, 1984). 
D~MN is formed with a low radiation chemical yield 
(G 0 =10-- 3 ) in dilute aqueous solutions (Ogura and Kondo, 
1967; Draganic and Draganic, 1980); however, as the 
concentration of HCN is increased {0.5 mole dm- 3 ), it 
becomes an important product (G 0 =0.45) in the irradia-
tion {Ogura and Kondo, 1967). 
1.4.2.2 Formation of larger molecules 
Between 50% (NfkCN, pH=9.2) and 79% (HCN, pH=6) of 
nitrogen and carbon atoms from decomposed starting 
46 
material are Luilt inLo Janre r rad:i olyti c prcxlucts. 
The oligorm?:rjc maLPri<iJs urnle ri:_ro some modifi cat:i ons 
during the radio] ysis, such a s hydrolysis and d ecar -
boxy]at, jon, and these mod1? 1cn"l.:icm s contr-:ilJuLe to the 
format:ion of' n lari:rer vnr.i el y of oligomcn-ic produ c ts 
(l>rc11i:anic nnd Dr?,11~anic:, lUU(: ). 
Ac id bydrolys is of Uw nonvolatile products 
re] eases several protu.i ni c und nonproteinic amin o acid~:; 
Th e compu~;j t, jun of amino acids in the 
Tab] e 1.3. G 0 of forroat,i()fl or amino H<: id~~l. 
- ---------?--? ------- - -- - ----
System 
Aru.in o a cid Il CN NH ... CN NaCN 
pll 6 pII =9 . 2 pH =ll.3 
-- ---- ----------------- ---- --
Ala O.OO!i 0.004 0 . 022 
Asp 0.0 12 0 . 010 0.008 
Gly 0.14 0 0 . 600 0.240 
Glu <0.001 <0 . 001 0.002 
Hi s 0.002 
Ser 0 . 002 0 . 005 0 . 018 
Thr 0.018 <0.001 <0.001 
Tota l 0. J f)() 0.620 0.290 
1. Dragan:ic et al., 1976a; and Draganic and Draganic, 
1977. 
47 
mixture does not depend strongly on the pH of system , 
but th~ir yi e lds do vary considerably depending on the 
initial pH of the solution (Table 1.3) (Draganic et 
al _, 1976a, 1977a; Draganic and Draganic, 1977). 
FracLionation of the nonvolatile material yield s 
basic (17% (HCN) and 38% (NfJ,,.CN) of total weight). 
acid ic 3% (HCN and NH.,.CN) of total weight) and neutral 
(69% (HCN) and 41% (NH4CN) of total weight) fractions. 
Th e analysis of the acidic fraction indi cates the 
l'I"f!'.;c?nce of dicarboxyl ic acids in the unhydrolyzed 
sample (Draganic et al., 1980; Niketic et al., 1983). 
Hydrolysis of these fractions releases several amino 
1:wids in diffe rent percentages: 83.9% in the neutral 
fraction; 13.8% in the basic fraction; and 2.3% in the 
acid fraction (Draganic et al . , 1980). 
The oligomers from ammonium cyanide (pH=9.2) and 
hydrogen cyanide (pH=6) solutions are very similar 
(Dracranic et al., 1980; Niketic et al - , 1982, 1983). 
At present, the following oligomers have been detected: 
Oli_gg_tmin~, -(CH:z NH)"-, is the main constituent of the 
neutral fraction, and represents 16.4% of the total 
It releases trace 
mixture of radiolytic products. 
amounts of amino acids upon hydrolysis, but it is not 
48 
c ] e ave d by proteolytic enzymes (Draganic et al . , 1980; 
Niket j c et a I . , 1982) . 
lS 
present in the neutral fra c tion, and represents 8.2% of 
t.b e toi...al mass of 1.,be mixture of produc Ls . After 
hydro lys i s , glyc ine is released, constituting 55% of 
the mass of the oljgome r. The oligomer lacks peptidic 
bonds, and upon hydrolysis ammonia is released 
(Dra~cmic et al . ,, 1980). 
Other oligome rs witb urea- aldehyde fragments have 
p e ptidi c bonds and are isolated in different fractions 
because of various side- chain modificat.ions present in 
They represent
t  h ue p  to oli  g 4o 0%m  e or fs  . the non-
The length of the
v  o pl ea pt -i -le radiolytic products. 
tidic fragments varies, but it is estimated to be up to 
30% of the oligomer mass (M.W . 5,000) in some neutral 
fract,ious (Draganic and Draganic, 1980). 
Olj,gomers wi th~p_tid_ic bonds""? The presence o:f these 
oligome rs was established based upon :four tests: 
Amino acid content on acid hydrolysis 
a. 
(Draganic et al., 1976a, 1977a; Draganic and 
Draganic, 1977}. 
49 
b. Positive biuret reaction (Draganic et al., 
1976a; Draganic and Draganic, 1977}. 
c. Infrared analysis (Draganic et al., 1977b) . 
d. Enzymal.ic c leavage wi l.b aminopepl.idas e M and 
pronase (Draganic et al., 1980; Nikctic et 
al., 1982). 
The oligomers are isolated from the bas ic fract.ion 
and rc"!present 5. 3% (NH"'CN) and 14-30% (HCN) of the 
toLal weight of the mixture of radiolyt.ic prcxlucts. 
Their moleeular weights are in the range 1,500- 20,000. 
Enzymati c treatment only cleaves 30% of the peptidic 
bonds (Draganic and Draganic, 1980; Niketic et al., 
1982). 
Some of thes e oligomers show catalytic activity 
as demonstrated by the hydrolysis of p - nitrophenylace -
tate ( pNPA ). The rate of hydrolysis9 of pNPA varies 
from 1. 0 to 7. 8 depending of the oligomer type, and is 
o:f the same order of magnitude as that of chymotryp-
sin1 0 (Niketic, 1984b}. 
9 Xl0- 8 mole (pNPA) s - 1 g- 1 (substance) . 
10 k(pNPA ? chymotrypsin} =3. 7X10- a mole s - 1 g- 1 ? 
50 
In spite of the prog ress made in the elucidation 
of products from t,b e :free - rad i cal oligomerization of 
UCN, furLh e r work i s s1, i l J needed to chara cterize the 
comp]ex mjxt,urc of r adjolyLic products. 
1 . 4 . 3 Hydrolysis vs oligomerization of HCN 
Sanchez et a 1 . ( 196 7) invest.igljt.ec.l Lhe extent of 
hydrolysis and i oni c o liaomerization of HCN in a basi c 
medium . They found that hydrolysis is the major reac-
Lion channel at conce ntration s ~ 0.01 mole dm- 3 HCN . 
Ionic oligomerization i s important at concentrations 
2 0. 1 mole dm- 3 HCN; t.h e ro 1.n: i mum conversion is centered 
at pH 9. 2, but, sharply f a ll c: at 8. 5 ~pH29. 8. Mixed 
kinetics occur in the range 0.01 - 0.1 mole dm- 3 HCN 
(Sanchez et al ., 1967) . 
Ogura et al . (1972) st,udied the fre e - radical olj -
gomerization of HCN in the p1 range from 1 to 10, and 
in the concentration range from 0.0005 to 0.1 mole dm- 3 
HCN. They found that the radiation chemical yield of 
d ecomposi-Lion of HCN is maxi mum (G 0 =6) in the pH range 
from 6 to 8 at concentrations of 0.006 mole dm- 3 HCN, 
and decreases to about half at 3~pH21 0. The authors 
also found that G 0 ( - HCN) i s not linearly r e lated with 
5l 
t,b e initial concentra t , j o n of HCN, and varies from about, 
3 -L o 9 . 5 i n t ,h e concentra1-ion range from 0. 0005 to 0. 1 
mo l e drn 5 . J,'ormj c a c:i d, a hydrolyzed produc t of HCN, 
is f ormc~d 1t1 low yie]cl (Ogura, 1968 ); howe v e r, its 
o r ig?jn .i s by fr ee rad i(;al r e act,:i ons (1.29, 1.34, 1.37), 
m,d ri uL by b a~;r ?d o r a c :id cata ]y~ed r e a c tion ~-; (1.43). 
Th e l iaGf-: and /or a c id C<:} L1-1 lyzed hydro] ys is of HCN :is 
j n :..; ir~n ifir, ,:rnL und e r the author's condit,ions since the 
r- a t .e of prod u c Lion of radicals in very high, : 5X10- s 
HO-
~' HC( =O)Nib ( 1. 43 a ) HCN ILO ff' _,_ _ .;. 
HC ( =O) NH::.: ( 1 . 4 3 l,) 
Tht : ra L e of hydrolys is of HCN by base or acid 
catalysis i s low; howev e r, 1,he la1,ter :i s more si~riifi -
c ant. The Arrhenius parame ters for the s e reactions 
h n v c b een r ccen1, ly repor1-ed by S-Lri bl ing and Mill er 
( 1 :1 8 7): for k =k o exp( - E,,. R- 1 1 1 ), whe re, 
k ,.., = 4 . 8X101 1 dm~- mole- 1 s - 1 , and .Ec. = (85. 0) kJ mole- 1 , 
in the base catalyzed reaction (1.43a); and, 
ko= l. 8X1Cf' dm"3 mole- 1 s - 1 , and .Ec. = (90. 4) kJ mole- 1 , 1n 
the acid catalyzed reaction (1.43b). 
52 
With the data given in the previous and present 
sections, we are in a position to evaluate the possible 
extent of hydrolysis and oligomerization of HCN in the 
primitive hydrosphere. Such an estimate has not yet 
been available in the literature; however, the kinetic 
p a rameters for the major processes are known. There-
f o r e , we can simplify such processes by a small set of 
simultaneous chemical equations {Table 1.4), and 
numerically integrate them with the use of a computer. 
The details of the computer program {ACUCHEM) are 
d e scribed detail in Chapter 2, section 2.7. 
Equations 1 and 2 in Table 1.4 are the equilibrium 
reactions for the dissociation of liquid water and HCN, 
respectively. The losses of HCN by base and acid 
hydrolysis are given by equations 3 and 4, 
successively. Equation 5 is the reaction leading to 
the ionic oligomerization of HCN. The production of 
radicals (R?) such as H-, HO-, and e..q- formed by 
interaction of various energy sources on the primitive 
hydrosphere 1s difficult to determine. If we only 
consider those produced. by radioactivity, and use a 
moderate energy flux of 20 J cm- 2 y- 1 (pages 14- 15, 
this study), the dose rate for the hydrosphere would be 
about 5Xl0-- 7 kGy s- 1 ? The total yield of radicals from 
53 
Chemical Equations used in Simulation. 
No. Equation Constant 1. 
J . Ib O fl()- + IJ-+- K=l. ox10- 1 "' 
2 . IICN -- cN + H. .. K=6. ox10- 1 0 
EhO 
3 . HCN -I fm? -+ IJCON[b -+ on- k =6. OXl 0-"' ,. 
H::- 0 c:: 
4 . HCN -I R? ? HCONib + w? 
r? 
k =2. 6Xl0- 1 1 rr,:??   
r? 
5 . BCN + -- cN Ion--oligomer k =2. 5X10- 7 
:1 
G. TL -0 R? k =5.2X10- 11 .=:.  
r 
7 . HCN/CN-- + R? FR--oligomc r k = l. OX10'3 C , 
, 
, 
8. 2R? R2 k = l.OX1010 r 
1 . Equilibrium or rate constants are distinguished by 
t.b e symbol Kor k, respectively. The units are 
s -- 1 , and dm3 moJe-- 1 s-- 1 for first and second order 
rat.e constants, consecutively. The values are 
cRlculated for 25?C from equations given in this 
chapter. 
radiolysis of liquid water 1s G=6. 4; however, if we 
conside r a low production, G=2, a rate of radical 
formation of 5. 2x10-- 11 s -- 1 is derived (equation 6). 
This calculation underestimates G (R?) from radiolysis 
of liquid water, and does not include the cont.ribution 
of other energy sources, which may have contributed 
54 
significantly {page 35). The rates of reactions of 
these radicals with HCN/CN- are all known {page 36 to 
39) , and we use a representative value of 108 dm3 
mo le- 1 s - 1 {equation 7). Dimerization of this generic 
radical (equation 8) has to be taken into account as a 
like ly competition for equation 7. The rates of 
radical - radical reactions from transients of water are 
all known (Buxton et al., 1988), and are typically ( 
C 
around 1010 dm3 mole- 1 s - 1 I ; therefore. this value was I I 
I 
used in the computer simulation. I 
The pH used in the simulation is 8, and this value 
is generally accepted for the primitive hydrosphere 
(Fox and Dose, 1977). As pointed out on page 22, we 
are not yet able to estimate the concentration of HCN 
in the primitive hydrosphere. A concentration range of 
0 . 01 - 0.1 mole dm- 3 was used as the upper limit in the 
computer simulation. Table 1 . 5 summarizes the net 
rates of hydrolysis and oligomerization via ions and 
free-radicals. The integration time was set for a 
relatively short period of time in geological terms, 2 
months in order to avoid over-decomposition of HCN. As 
it is evident from these results, the decomposition of 
HCN is primarily via free - radical oligomerization reac-
tions, 288%, at concentrations ~10- 3 mole dm- 3 ? Hydro-
lysis is unimportant (~12%), but ionic oligomerization 
55 
Table 1.5 . Percent Relative Rates of Hydrolysis and 
Ol igomeriza~ion o f HCN for the Primitive Hydrosphe r e . 
HCN Hydrolysis Oligomerization 
Ioni c Free- Radical 
1. ox10- 4 0 . 5 <0.1 99.5 
1 . ox10-::s 11. 5 0.1 88 . 4 
1. ox10- 2 54.1 2.8 43 . 1 
1.ox10- 1 60.0 31. 5 8.5 
is negligible {~0.1). Oligomerization via ions could 
b e come significant only at high concentrations {~ 0.1 
mole dm- 3 ), but under this conditions hydrolysis also 
enhance s . 
1.5 Research objectives 
Great progress has been achieved in the under-
standing of mechanisms and efficiencies of HCN produc-
tion triggered by ultraviolet light, ionizing radia-
tion, and pyrolysis. The contribution of electric 
discharges to the synthesis of HCN in the primitive 
atmosphere is generally considered significant (Miller 
56 
and Orgel, 1974). Nonetheless, no accurate evaluation 
of such a contribution has been presented. The major 
obstacle has been the inability to measure the amount 
of energy transferred from the high-voltage, high- fre-
quency electric discharges. 
Our research goals were centered in obtaining a 
better insight into two major aspects of role of 
hydrogen cyanide in chemical evolution . In particular, 
one of these was to accurately measure the chemical 
yield of formation of HCN in the electrolysis of a 
simulated primitive atmosphere and to elucidate its 
me chanism of synthesis. This work is described in 
chapter 3 . 
The other maJor research goal was to investigate 
the effect of cyanocomplexes of transition elements on 
the free- radical oligomerization of HCN. Specifically, 
we were interested in hexacyanoferrate(II) and (III), 
since they probably accumulated in the primitive 
oceans (section 1.3, this study). There is great in-
terest involved in this investigation since only a 
limited number of studies in abiotic chemistry has been 
devoted to examine the effects of metal ions in 
catalyzing reactions of significance to the origins of 
life (Kobayashi and Ponnamperuma, 1985a). The limited 
57 
reports indicate that metal ions could significantly 
increase the yields of prebiologically and/or bio-
logically important compounds from a variety of abiotic 
type reactions (Beck, 1978; Kobayashi and Ponnamperuma, 
1985b). The systems HCN/Fe were ~-irradiated to 
trigger free - radical reactions in aqueous solutions, 
and various mixing ratios for iron were investigated 
ranging from 100.00 to 0.01%. The results and 
implications of this work are described in chapter 4. 
A general discussion and conclusions of all the 
data is given is chapter 5. 
58 
CHAPTER 2 
EXPERIMENTAL PROCEDURES 
2.1 General 
Al l chemicals were of the highest purity comme r -
cial ly available, and were used without further purifi -
cation un l ess otherwise stated . Their sources were: 
Ald r i c h Chem. Co . , Inc.; Allied Chemical; Eastman 
Kodak, Co; Air Products & Chemicals, Inc . ; EM 
Industries, Inc . ; Fisher Scientific Co.; J.T. Baker 
Chem . Co.; Mallinckrodt, Inc.; Matheson Gas Products; 
Sigma Chem . Co. Methanol and benzene were purified 
according to the procedures of Perrin ?t al . (1966). 
Deionized-distilled water was used for cleaning 
of glassware and for analysis of irradiated (electric 
discharge or ~-irradiation) samples. It was purified 
by flowing tap water through a Millipore system (Mil-
lipore, Co.) consisting of charcoal activated and 
59 
anion- cation exchanger cylinders, and finally distilled 
into a glass container . 
Tr i ple distilled water was used for preparation 
and irradiation of samples . This was obtained by 
succ essive distillations from an alkaline { pff:, 10) 
solution of 0.01 mole dm- 3 potassium permanganate, an 
acid {p[?:F=2 ) solution of 0. 01 mole dm- 3 potassium 
dichromate, and finally distilled without reagents 
{Draganic and Draganic, 1971). In all cases, only 
f res hly prepared water was used. 
All glassware was made of borosilicate glass 
{"Pyrex"), and was cleaned according to standard 
procedures used 1n radiation chemistry {Swallow, 1960) . 
These consisted of immersing the glassware in concen-
trated sulfuric acid and warm 7 mole dm- 3 nitric acid, 
followed by their abundant washing with tap water, 
deionized- distilled water, and triple distilled water, 
and finally dried overnight at 2200?C in an oven . 
2.2 Preparation of electric discharge samples 
Three gaseous systems were investigated. A mix-
ture of C~ - Nz - IkO was used to simulate an early primi -
60 
tive atmosphere. This system has been extensively used 
in this laboratory to obtain basic information on 
abiotic synthesis of amino acids {Kobayashi and Ponnam-
peruma, 1985b). The other systems consisted of gaseous 
CH4, and air {N:z - 0.Z); these were used to study the 
properties of electric discharges. 
C 
C 
r 
2.2.1 Clk-N:z-EkO system rr  
'r  
El e ctric discharge experiments of a simulated 
primitive atmosphere were performed using a 4.3 dm3 
dumbbe ll shaped flask {Figure 2 . 1). 0 . 1 dm3 of 0. 05 
mole dm- 3 ammonium chloride buffer at pH 8.7 was 
Figure 2.1. Electric Discharge apparatus. AC: Alter-
nating current power; Cl: Coil; Cr: Condenser; E: Elec-
trodes; G: Ground; H: Heating tape; HM: Heating 
mantle; I: Vacuum and gas inlet; MS: Magnetic stirrer; 
T: Transformer. 
61 
filtered through a Millipore membrane (pore size 0.22 
u m, type GS) and then introduced into the flask. The 
syste m wa s air-evacuated by a diffusion vacuum pump. 
The gases dissolved in the ammonium chloride buffer 
solution were removed by 4 freeze - thaw cycles while the 
va c uum pressure was maintained at 30 mTorr. 200 Torr 
of me thane (Matheson Gas Products) and 200 Torr of 
nitrogen (Air Products & Chemicals, Inc.) of purity 
299.99%, were introduced into the flask to yield a 
gaseous solution of 0.0108 mole dm- 3 of methane, 0.0108 
mole dm- 3 of nitrogen, and 0.00782 mole dm- 3 of water 
vapor after allowing the system to equilibrate at 60?C 
prior to electrolysis . 
2.2.2 e&.. and air (N:z/0:z=3.7) systems 
These systems were prepared in a 4.3 dm3 dumbbell 
shaped flask (Figure 2.1) or in a 2.1 dm3 round flask. 
Air taken directly from the atmosphere was introduced 
into the flask and the pressure was adjusted from 1 to 
760 Torr with a pressure gauge. Methane (Matheson Gas 
Products) systems were prepared by removing the air 
from the flasks with a vacuum diffusion pump to about 
50 mTorr, followed by filling with methane gas of 
purity 299.99%,, and its re-evacuation. The flasks 
62 
were filled with methane at 200 or 760 Torr. 
2.3 Preparation of ~-irradiated samples 
Aqueous , oxygen- free, 0.1 mole dm- 3 HCN solutions 
containing {10- 3 - 10-e mole dm- 3 ) potassium hexacyano-
ferrate{II) or {III) at pH~ 6 can be conveniently 
prepared using a simple setup {Figure 2 . 2). 0.3 dm3 of 
triple distilled water or an aqueous solution of (10-e _ 
9 
1 
2 3 
LI 5 
Figure 2.2. Preparation of Oxygen- free Aqueous Solu-
tions of HCN. 1. Argon cylinder; 2. Tank containing 
triple distilled water; 3. Reactor vessel containing 
aqueous sulfuric acid (1/1 v); 4. Syringe filled with 
saturated aqueous KCN or NaCN solution; 5. Syringe for 
injecting or removing sample solution; 6. Vessel con-
taining HCN sample; 7. NaOH or KOH pellets; 8. Satura-
ted NaOH or KOH solution to trap undissolved HCN; 9. To 
hooo extractor. 
63 
10- 3 mole dm- 3 ) potassium hexacyanoferrate(II) or 
(III) (Fisher Scientific Co. or Allied Chemical, res -
pectively) is placed into a vessel (6 in figure 2.2), 
and the solution is degassed at room temperature by 
bubbling with 99.998% argon (Air Products & Chemicals, 
Inc .) for at least 30 min. HCN is generated in the 
reactor vessel (3) by slowly intrcxlucing 0.01 dm3 of a 
degassed saturated NaCN or KCN (98.5% purity from J.T. 
Baker Chem. Co.) solution (4) into 0.02 dm~ of degassed 
sulfuric acid (J.T. Baker Chem. Co.) solution (1/1, 
v/v). Gaseous HCN is intrcxluced into the sample flask 
(6), and the concentration of HCN is monitored by 
withdrawing aliquots with a syringe (5). Undissolved 
HCN is trapped in containers (8) with saturated KOH or 
NaOH. 
Aqueous, oxygen- free, 0.02 mole dm- 3 potassium 
hexacyanoferrate(II) (Fisher Scientific Co.) solutions 
(pH 6.7) were prepared using the same setup (Figure 
2.2), except that HCN was not generated. 
0.01 - 0.10 dm3 deoxygenated solutions of HCN and/or 
hexacyanoferrate{II) or {III) were prepared just prior 
to irradiation and were kept in special borosilicate 
glass syringes with caps during irradiation. When 
larger amounts of sample were needed for analysis, the 
64 
solution was introduced into special Pyrex vessels 
(0.45- 0 . 75 dm3). These vessels permitted gaseous 
radiolytic products to escape from the system prevent-
ing a build- up of an over-pressure above the liquid 
phase, and precluding air from entering into the solu-
tion. 
2.4 Irradiation of samples 
2.4.1 Electric discharge experiments 
The electric discharge across two electrcxies 
separated by a 0.1 dm gap was produced using high fre-
quency generators (Tesla coils) from Electro-Technic 
Products, Inc. Three different Tesla coils were used: 
Two were model BD-50 (A and B) and one was model BD-
50E. The electrodes were made from 0.13 mm diameter 
tungsten rods from Laboratory Supply & Equipment Co. 
The intensity of the discharge was controlled by 
the output adjustment knob of the Tesla coil. In order 
to determine the amount of energy introduced by an 
electric discharge, we investigated the properties of 
the electric discharge at various spark gaps (0-0.1 dm) 
65 
and pressures {1-760 Torr) in three gas systems: air, 
CH,. - ~ - fk O, and CH. ... 
Three different methods were developed to deter-
mine the amount of energy introduced into the systems 
by the electric discharge. The first was an indirect 
me thod, the che111ical dosi?eter {Navarro-Gan~ lez et 
a 1 . , 1986). This consisted of measuring the extent of 
decomposition of methane produced by the electric dis-
charge and correlating it with a study where both the 
energy input and extent of decomposition of methane 
were measured. The other two were direct methods and 
consisted of measuring the voltage and current of the 
electric discharge with an oscilloscope and by calori -
metry . The energy input per mole {E~) was calculated 
as E~ - IVtn- 1 ; where I and V are the discharge current 
and voltage, respectively, tis the reaction time, and 
n is the number of moles of the gas present. In order 
to ascertain the effectiveness of the calorimetric 
method reported by Stribling and Miller {1987), we also 
measured the energy input of the electric discharge 
according their procedure. 
Energy measurements using methane as chemical dosi-
meter. In a chemical dosimeter the energy input is 
determined from the chemical change produced in a sub-
66 
stra1-e. Calculation of the energy input requires a 
knowledge of the chemical yield (G) for the reaction or 
product, which is found by comparing the chemical sys -
tern with some form of absolute dosimeter. Prior to 
1986, absolute dosimetric methods of high voltage high 
frequency electric discharges were not available. 
Absolute dosimetry for low voltage electric discharges 
has long been recognized (Wiener and Burton, 1953), in 
which the energy input per mole (E~) was calculated 
from the discharge current and voltage. Wiener and 
Burton (1953) studied the electrolysis of methane at 
atmospheric pressure using a low voltage (~500 volts) 
direct current electric discharge. They measured the 
yields (G) of decomposition of methane and formation of 
acetylene, the principal product, as a function of 
energy input. Since this system is very simple to 
reproduce in the laboratory, we proposed its use as an 
indirect method to determine the energy in the high 
voltage electric discharge experiments (Navarro--Gon-
zalez et al., 1986). Figure 2.3 shows graphically the 
raw data obtained by Wiener and Burton (1953). The 
extrapolation of G 0 was obtained using different type 
of polynomial regressions, and the best estimate was 
67 
2.0 ?--
......, 
i 8 1.5 
....... 
.-.1.?  t.O 
Q 
3 
1.0 2 .0 s.o 4 .0 
0.6 
b 
~ 0 .. ( 0 
~ 
..........  D.'1 
0 ,0-t--- -------~---i 
0.0 0.6 1.0 1.6 2.0 
Figure 2.3. Energy Dependance of the Decomposition of 
Me thane (a) and its Chemical Yield (b) in the Atmos -
pheric Electric Discharge of Methane. Raw data was 
taken from Wiener and Burton, 1953. 
G 0 ( - CH~) =8.34, with an error of 20%. The power (P) 
of the high voltage electric discharges can be deter-
mined by measuring the rate of disappearance of 
methane, k (-C~), and is calculated according to the 
following expression: 
68 
p -
rges 
 introduced (E1) b
y electric discha is 
The energy
- 1 ? 
computed by E1 =
pt n
ents with an oscillo
scope. 
measurem
fultage and curre
nt 
ge and current of
 
the volta
The circuit for m
easuring 
 shown in figure 2.
4. 
is Vo
ltage 
 
the electric disch
arge
R1 
TC 
VM 
CM 
DM Rz 
AC 
=G 
c Cir-
chematic Represen
tation of Electri . 
Figure 2.4. S re
nt
ring the Discharge
 Voltage and Cur
its for Measu urr~nt measuremen
t; 
cu rrent power; CM: C
AC: Alternating c
u
ital_mult1meter; G
: 
DC: Discharge cham
ber; DM: Dig
coil; VM: Voltage : Tesla 
Ground; R: Resist
ors; TC ~.R:z22.0 k Q; 
~easurement. 20.0<
Ri20.5 MD; 10.0
-
lOOQ~}hL 50 D.. 
69 
ark discharge were ma
de with a 
measurements of the 
sp
tenfold attenuator 
Tektronix 515A oscill
oscope using a 
lectricity supplied t
o 
The e
Probe (PG105 Tektron
ix}. 
 was 
Tesla coils was 120 V
 and 0.1-0.3 A, and
the 
020 B digital multim
eter from John 
measured with a 8
 resistors (R} used w
ere of 10 
F'luke MGL Co . , Inc. 
The
%. 
W Power rating with a tol
erance of 2-5
 discharge were con-tric
Resistor 1 and the e
lec
allel to the voltage 
source and the same 
nected in par
ting path. The high  conduc
Voltage was applied 
to each
and 
the output was attenu
ated by resistor 1 
Voltage of 
tor 2. 
sultant voltage was m
easured across resis
the re
ies, the 
e resistors 1 and 2 w
ere connected in ser
Sinc
e in this path was th
e same. The 
current everywher
was, 
output voltage of the
 Tesla coil (Vo} 
 difference measured 
across 
here, Vm is the potentia
l
W
sistance of R1 and 1k
 was varied 
resistor 2. The re
.0 k fl, respective-
from 0.5 to 20.0 M ~
. and 2.0 to 10
ly_ 
70 
t (I~) supplied by the
 Tesla coil 
The output curren
arge and the path 
Was split between the
 spark disch
nts in both 
containing R1 and Rz. The sum 
of curre
is -
l paths was equal to I
~. Since the spark d
Paralle
current 
harge was connected in
 series with Ih, the 
c
e same at every point
 in this path. The voltage 
was th
measured in order to d
etermine the cur-
across 1h was 
 this path. The curre
nt supplied by the 
rent through
Tesla coil was, 
oss 
Vm' s the potential diff
erence measured acr
Where, 1
 to 
. The resistance of R
:s was varied from 50
resistor 3
1000 Q 
orimetry. 
fultage and current m
easurements by cal
ltage 
2.5 shows the set up u
sed to measure the vo
Figure 
the electric discharge
 by calorimetry. 
and current of 
nitored by the 
The heat dissipated (Q1
) from R1 was mo
r1?metric box made of 
temp erat  
lo
ure ri? se 1? n 
a ca
 temperature was meas
ured with a 
Polyurethane. The
nce thermometer from 
moctel 9540 digital pla
tinum resista
71 
T 
TC 
DM 
p 
AC 
C 
xperimental Layout fo
r Measuring the 
Figure 2.5. E  by Calorimetry. AC:  Discharges
Energy Input of Elec
tric
current power; C: Ca
lorimetric box; DC: 
A~ternating multimeter; G: Ground
? 
Discharge Chamber; D
M: Digital al therm~-
hermometer probe; R: 
Resistors; T: Digit
P : T 5 k D. 
eter; TC: Tesla Coil. 
500~R1220 k D; R::z=
m
of 
h an accuracy of 0.00
3?C. The voltage 
Guildline wit
ccording to the follo
wing 
the discharge was ca
lculated a
equation: 
e was obtained from t
he 
The current of the di
scharg
from both R1 and R::z, 
and was 
heat dissipated (Q 1 ? 2
) 
following expression:
 
Calculated according
 to the 
72 
0
I _ [ _Q_-_<_vz_Rz_l_R_i_) J ? ~ 
The res istance of R1 and Rz were varied from 20 to 500 
k D ; and 5 k ~ . respectively. 
Energy determination by calorimetry. This method was 
suggested by Stribling and Miller {1986, 1987). It 
consists of measuring the rise of temperature in the 
ealorime t-ric box produced by the sparking of the 
electric discharge sample {Figure 2.6). The amount of 
TC 
- G 
p 
C 
Figure 2.6. Measurement of Heat Generation by the 
Electric Discharge according to Stribling and Miller 
{1987). C: Calorimetric box; DF: Discharge Flask; E: 
Electrode; G: Ground; P: Thermometer probe; T: Ther-
mometer; TC: Tesla Coil. 
73 
energy introduced by this methcxl is not accurate since 
several aspects not taken into account are the energy 
converted into chemical form, or into light or not 
absorbed by the gas. Gases have a low collisional mass 
stopping power when they are irradiated with low energy 
electrons {Spinks and Woods, 1976), as in the case of 
electric discharges. Therefore, the methcxl of Miller 
and Stribling underestimates the amount of energy 
supplied by electric discharges; however, we also 
measured the energy of our experiments with this methcxl 
in order to compare its effectiveness. 
2.4.2 ~-Irradiations experiments 
~ - Irradiations were carried out using three radio-
active 6 ?Co units located at the Institute of Nuclear 
Sciences, Universidad Nacional Autonoma de ~xico 
{U . N.A.M.) at Mexico City (dose rates of 0.7 and 20 kGy 
h- 1 ) and the Department of Chemical and Nuclear 
Engineering, University of Maryland (U.M.) at College 
Park (dose rate of 36.6 kGy b- 1 ). The irradiation dose 
was varied from 0.014 to 600 kGy. 
74 
The irradiations were initiated at room tempera-
ture. The temperature of the samples did not increase 
during its irradiation at low dose rate (0.7 kGy h- 1 , 
U. N. A. M. ); however, it increased up to 45?C or 55?C 
when the samples received a total dose of 80 kGy using 
dose rates of 20 kGy h- 1 or 36.6 kGy h- 1 , respectively. 
Figure 2.7 shows the variation of temperature as a 
function of dose produced by the 0 ?Co source located at 
U. M. The increase in temperature during the irradia-
tion of the aqueous solutions does not lead to a sig-
nificant effect on the radiation chemical yield of 
decomposition of liquid water, G 0 (-EkO); G 0 (-Ek0) 
60 
0 
0 
._,, 
Q) 
L 
:::, 
+' 40 
0 
L 
t> 
Q_ 
F 
t> 
f-
20 
0 50 100 15C 
Dose ( kGy) 
Figure 2.7. Dose dependance of temperature in the ~-
irradiation of aqueous dilute solutions. 0 ?Co source: 
Department of Chemical and Nuclear Engineering, Univer-
sity of Maryland at College Park. 
75 
ly from 4.41 at 23?C to 
4.54 at 65?c and 
varies slight
.07% per degree (Dragan
ic and Draganic, 
increases 0
rate 
1971). The effect of temperatur
e on reaction 
ts is also not large, in
creasing only by a few 
constan
nd Draganic, 
tenths of a percent per
 degree (Draganic a
1971). 
2.5 Control experiments
 
 samples were prepared a
nd analyzed simul -
Control
ey were 
taneously to irradiated
 samples except that th
ubmitted to electrolysis
 or radiolysis. The 
not s
 absence of 
analysis of these sampl
es corroborated the
d the analysis 
contamination during the
 preparation an
of the samples. 
2.6 Analyses of samples 
eir 
The samples submitted to
 irradiation and th
diately after irradiation
 
controls were analyzed 
imme
 below. 
according to procedures 
described
76 
2 6 Determination of gas 
products 
- -1 
gas from the electric
 
3 
An aliquot of 0 . 05 dm
of 
harge 
ct ? arge sample was transfe
rred from the disc
lsch
iner and 
flask to a high- vacuu
m sealed gas conta
on-
a model 21-620A mass 
spectrometer from C
analyzed by 
ics Co. The gases we
re iden-
solidated Electrodyna
m
porting 
ied by their fragmen
tation pattern. Sup
tif
eir identity was obta
ined by gas chroma-
evidence of th
 reported previously ample, and was
tography of the gas 
s
gas 
obayashi and Ponnampe
ruma (1985b). The 
by K
were quantified by th
e intensity of the 
Products 
the 
inant fragment ion wh
en 
molecular ion or a p
redom
d by a dif-
ormer overlapped wit
h a fragment produce
f
 of 
nt Table 2.1 summari
zes the sensitivities
fere gas. 
spectrometry. Ethyle
ne 
th he mass
 
e different ions in 
t
-, 
antified because its 
molecular ion (C:z&..
Was not qu
t (C2H3+, 27) overlap
ped 
2 ) and the predominan
t fragmen
8
+, 28). 
ith those of ethane a
nd also nitrogen (N2
W
olution and 
Dissolved gases were
 extracted from s
-
 a mass spectrometer 
(Consolidate Electro
injected into
s chromatograph 
dynamic s c o. ) 
00 ga
or 1? nt  o a Varian
 14
ivity detector (Varia
n 
equipped with a therm
al conduct
ied Toepler pump acco
rding to a 
Associates) by a mod
if
Torres et al., 1982; 
Procedure already de
scribed (
77 
Tab le 2 . 1 . Sens itivity fa c tors fo r ions in the mass 
spectrome ~ ry ana lys is . 
Parent Molecule Frag me n t Se n s it i vity 
(MW) Factor1 
CH.,._ Cfl.,. + (16) 2.1 
C2Ek <aw (25) 3 . 1 
C2 H2 + (26) 14.1 
C2 H.,._ (aH.,._ + (28) 8 . 3 
C2 Ho (af:b + (30) 2.7 
N:2 ~ + (28) 2.9 
1 . Se n s itivity factor is defined as the peak he i ght 
p e r pres sure of gas samples . 
Casti llo, 1983) . A column (12 dm long, 0 . 06 dm e . d . ) 
pac k ed with silica- g e l (40/60 mesh) from Varian 
Associates was used to chromatograph hydrogen or carbon 
dioxide u s ing argon or helium (Air Products & Chemicals 
I n c . ) wi th a flow rate of 0.03 dm3 mi n- 1 ? The tempera-
t u r e regime was isothermal at 50? or 55?C, con-
s ecutively . 
NH3 and CO:z were identified by mass spectrometry; 
Ek and CO:z were identified and quantified by gas 
chromatography. Figures 2.8 and 2 . 9 show the calibra-
78 
l() 
0 3.0-.------ --- --------~ 
X 
n 
I 2.0 
l: 
"O 0 
., 
ci 1 .O -
E 
.--, 
N 
:r: o.o------~-- -----------l 
L...-1 0.0 0 .2 0 .4 0.6 0 .8 
Height per moss ( cm ? g- , ) 
Figure 2.8. Calibration Curve for the Microdetermina-
tion o:f dissolved fk in Irradiated Aqueous Solutions. 
Calibration system: 0.02 mole dm- 3 ethanol (pH 7) . 
Lr) 
a 
X 
n 
I 
E 
-0 
., 
0 2.0 
...E...,  
.--, 
6' o.o?-----~- ---~-------l 
u 0.0 0. i 0.2 0.3 
L...-1 
Area per moss ( cm2 - g-1 ) 
Figure 2.9. Calibration Curve for the Microdetermina-
tion of dissolved CO:z in Irradiated Aqueous Solutions. 
Calibration systems: 5.0Xl0-4 mole ?dm- 3 ( 0 ); and 
2.5Xl0-4 mole dm- 3 ( 6 ) sodium formate; and 7.5Xl0-4 
mole dm- 3 oxalic acid ( ? ). 
79 
obtained accordi
ng the 
ion curves for 
Ek and CCk 
t
l. (1982) and C
as-
by Torres et a
Procedures desc
ribed 
tillo (1983). 
ination of ammon
ia 
2 -6.2 Determ
ry (sec-
 identified by m
ass spectromet
Ammonia was ar-
etermination wa
s c
tion 2.6.l). Its qu
antitative d
from 
an ammonia selec
tive electrode 
ried out using  pH meter 
-12) connected t
o a model PHM84
Orion (model 95
ntials of both a
n 
Radiometer. The 
electrode pote
from olution 
ple (P ) an
d a reference s
irradiated sam Sample  after 
mole dm-
3 NH4Cl were deter
mined
(PR O
 1 
eference
) ' ?  12 with a 5 
e pH of the solu
tions to above
adjusting th onia 
ion. The conce
ntration of amm
ut
mole dm- 3
 NaOH sol
ord-
e was determined
 acc
(CNfh) in the ir
radiated sampl
 to the followin
g equation: 
ing
4 ple)] 
2 - 1.09X10- (P
Reference PSam
[ 3.7
= 10 
rried 
monia electrode 
was ca
The calibration
 of the am
2 
to 10- mole dm
-3 , 
n the concentra
tion from 10-e 
out i
80 
and the correlation coefficient for fitting the data 
to the derived equation was 0 . 998. 
2.6.3 Determination of hydrogen cyanide 
Gaseous HCN in the electric discharge experiments 
was dissolved in the aqueous phase by adjusting the pH 
of the solution to about 11 with a 1 mole dm- 3 sodium 
hydroxide solution, and allowing the system to equi-
librate for 1 hour at room temperature. 
An aliquot of the liquid phase of the samples was 
injected directly into a Perkin Elmer model 990 gas 
chromatograph equipped with flame a ionization detec-
tor. The column used for the analysis was made of 
stainless steel (12 dm long, 0.03 dm external dia-
meter), and was packed with Chromosorb 102 (80/100 
mesh) from Varian Associates. The program temperature 
was from 60 to 200?C at a rate of 6?C min- 1 ? Nitrogen 
or helium (Air Products & Chemicals Inc.) were used as 
the carrier gases with a flow rate of 0.03 dm3 min- 1 ? 
HCN was identified by its retention time (~ 7.8 min), 
and by its coinjection with a standard HCN solution. A 
calibration equation was derived for the quantitative 
determination of HCN : 
81 
7 
CHCN = 1.69X10-- Pa 
where, ~CN is the concentration of HCN in the sample; 
and Pa is peak area converted to attenuation factor 1. 
The calibration curve for HCN was carried out in the 
3
2 
concentration from 10--e to 10- mole dm- , and the 
correlation coefficient for fitting the data to the 
d er1. ved equation was 0.988. 
Quantitative determination of HCN was also carried 
out by titrimetric analysis of the aqueous solutions 
using a 0.05 mole dm- 3 AgNCb (Allied Chemical) aqueous 
In order to get a sharp end-
solution {Bassett, 1978). 
Point, iodide ion was used as the indicator according 
to the method of l)eniges (Bassett, 1978); the titration 
Procedure consists of adding AgN<h: to the HCN sample 
3
contained in an ammoniacal solution {0.2 mole dm- ) in 
3
the presence of iodine ion {KI, 0.01 mole dm- ) until 
the solution becomes turbid due to the precipitation of 
silver iodide. 
HCN was also identified and quantified with a 
cyanide selective electrode {model: F1042CN) and a 
reference Calomel electrode {model: K401) connected to 
82 
a pH me ter {model PHM84) from Radiometer. The elec-
trcxle potential of the samples was obtained after 
adjus ting the ionic strength {0.1) and the pH {ll) of 
the sample with a 1.8X10-3 mole dm- 3 NaHC(b and 
3. 2x10--:cs mole dm- 3 Naz CCb aqueous solution. A 
calibra-
tion equation was derived for the quantitat 1?ve analysis 
of HCN: 
[ (1. 72X10- 2 PS amp l e + 6 ? 38) ] 
wh e re, ('_ _ CN is the concentration of HCN; and p is 
-H Sample 
the electrode potential of the sample. The calibration 
of the cyanide electrode was carried out in the con-
centration from 10-0 to 10-4 mole dm- 3 , and the 
correlation coefficient for fitting the data to the 
derived equation was 0.999. 
Calibration curves for the determination of HCN in 
solutions containing up to about 0.1 mole dm- 3 
chloride ion were also obtained; however, the calibra-
tion equations and factors did not change. 
83 
2.6.4 Determination of hexacyanoferrate(II) and (III) 
He xac yanoferrate(II) was dete rmined by its 
qu a nt itat ive oxidation by eerie sulfate (Day and 
Underwood , 1980): Few drops of indicator, diphenylamine 
(1% in H:zS04 c ) we re added to an aliquot of irradiated 
so lution and titrated with a eerie sulfate solution 
(0.01 mole dm- 3 Ce(S0..)2.2(NH4)2S0....2H:z0 in 0 . 2 mol e 
dm- 3 aqueous H:z~) until a sharp color change to a 
d eep blue- brown took place. 
He xacyanoferrate(III) was determined spectros-
c opica lly at its absorption maximum centered at 420 nm, 
wh e r e, its absorption coefficient was experimentally 
d e termined to be: 1020 dm3 mole- 1 cm- 1 at 25?C . Hexa-
cyanoferrate(II) absorbed insignificantly under this 
c onditions, ? 420 ~ 9 dm3 mole- 1 cm- 1 at 25?C . 
2.6.5 Determination of aldehydes and ketones 
Aldehydes and ketones were analyzed by direct 
injection of the irradiated samples into a Perkin Elmer 
model 990 gas chromatograph equipped with a flame 
ionization detector. The chromatographic conditions 
are similar to those described in section 2.6 . 3 for the 
84 
gas-chromatography of HCN, and have been 
reported in 
d etai l elsewhe r e (Negr6n - Me ndoza et al . , 1983, )_ 
1984
Aldehydes and ketones were converted via 2, 4 -d.i -
nitrophe nyl - hydrazine (DNP) into 2,4- dinitrophenylhy-
draz ones (DNPH), and were analyzed by p a p e r chrom t 
a og-
raphy (Navarro- Gon~lez and Negr6n- Mendoza. 1983a) or 
g as chromatography (Navarro-Gonzal e z and Negron- Men-
d oza , 1983b} according to procedures already described . 
DNPH of aldehydes and ketones were also identified by 
mass spe ctrometry (VG Analytical, LTD model 7070E) 
using electron impact or chemical ionization (with 
isobute n e ) techniques at 70 eV. Their fragmentation 
p a t t ern wa s compared with those of standard aldehyde 
d e rivatives and published MS spectra (Stanley et al .. 
1975). 
Calibration curves were obtained for DNPH deriva-
t ives of HCHO, CH3 CHO, CfbCfkCHO, and CfbCOCfb were 
c arrie d out in the concentration range 10-3 to 10-2 
A general calibration equation was derived : 
CRCHO = mP 
85 
where CRCHO is the concentration of aldehydes; Pis the 
peak height in cm at attenuation 1; and mis the slope 
of the calibration curve and were (mole dm- 3 cm- 1 ): 
2.83X10- 0 {HCIIO); l.79X10-0 (CfbCHO); and l.lOXl0- 0 
( CH3 Cti;, CHO and CH'.5' COCl:h ) . The R2 values were equal or 
greater than 0.984. 
2.6.6 Determination of polycarboxylic acids 
Polycarboxylic acids were analyzed by gas- liquid 
chromatography as their methyl esters according to a 
procedure already described (Negron- Mendoza and Navar-
ro-Gonz~lez, 1982; Negron- Mendoza et al., 1983). The 
columns used for the analyses were packed with 10% 
Reoplex 400 {Anspec Co., Inc.) or 3% OV- 17 (Supelco, 
Inc.) on Chromosorb W (A.W., DMCS, 80/100 mesh) from 
Supelco, Inc. The chromatographic conditions were as 
described previously (Negr6n-Mendoza and Navarro-Gon-
z~lez, 1982; Negron-Mendoza et al., 1983). Dicar-
boxylic methyl esters were also analyzed with a 
Hewlett- Packard model HP5790 gas chromatograph coupled 
to a mass spectrometer (VG Analytical, LTD model 7070E) 
operated at 70 eV. A 25 m X 0.25 mm I.D. glass 
capillary column was used with bonded methyl 5% phenyl 
silicone from Perkin-Elmer. The carrier gas was 
86 
helium with a flow rate of 0.00042 dm3 min- 1 ? The 
temperature was increased from 60?C to 200?C at l0?C 
Calibration curves were ob~ained in the concentra-
tion range from 10-2 to 10-4 mole dm-3 , and a general 
calibration equation was derived: 
where CRCCkH is the concentration of carboxylic acids; 
A is the area of the peak; and mis the slopes of the 
calibration curves and are given in Table 2.2. 
87 
Table 2.2. Slopes (m) of calibration equations
p  o fl oy rc  arboxylic acids. 
Acid mi 
Lacti c , oxalic and pyruvic 2 . 44 
Succinic 0.45 0.992 
GlutRric 1.02 0.999 
Pimelic 0.75 0.998 
Aconitic 0.50 0 .999 0.998 
2.6.7 Determination of oligomeric material 
Oligomeric material, as referred in this study, is 
any non - volatile product tha~ originates from solute 
molecules reactions initiated by irradiation. 
Water insoluble oligomeric material produced by 
the sparking of a simulated atmosphere was filtered 
through a Millipore membrane (pore size 0.22 um, type 
GS) and freeze - dried. Non-volatile radiolytic products 
from HCN/Fe mixtures were obtained by freeze-drying of 
the irradiated solution. The yield (g dm- 3 ) of 
oligomeric material was measured with a GRAM- ATIC 
balance from Mettler Instrument Co. Elemental analysis 
88 
of this material was obtained in order to determine 
its radiation chemical yield (G) in terms of carbon 
and/or nitrogen atoms converted into prcxlucts. This 
analysis was performed by the staff members of the 
elemental analysis facility of the Department of 
Chemistry of the University of Maryland at College 
Park. 
2.7 Radiation chemical yields: G 
The radiation chemical yields of prcxlucts and 
solutes were expressed as the number of molecules 
formed or destroyed per 100 eV of energy absorbed 
(Spinks and Woods, 1976), and were calculated from the 
slopes of concentration-dose plots (Ogura, 1968) ac-
cording to the following expression: G=FS; where Sis 
the slope of the curve in mole dm-3 kGy- 1 , and Fis 
9.6485X1D3 or l.5292Xl04 molecules mole- 1 cm-3 kGy for 
o- irradiated or electric discharge systems, 
respectively. 
89 
2.8 Computer simulation of the chemical sy t 
s ems 
Computer modeling is one of the most Powerful 
tools for the quantitative understanding of highly 
complex chemical reaction systems (Braun et al., )_ 
1988
Re cently W. Braun and J.T. Herron from the Chemical 
Kinetics Division, and D. Kahaner from the Scientific 
Computing Division of the National Institute of Stan-
dards and Technology (Gaithersburg, Md.) have released 
an effective computer package named ACUCHEM, that is 
especially suitable for the numeric integration complex 
chemical rate equations. ACUCHEM is designed to 
operate on the IBM Personal Computer family and com-
patibles . It is a program for solving the system of 
differential equations describing the temporal behavior 
of spatially homogeneous, isothermal, multicomponent 
chemical reaction systems. Zeroth, first and second 
order reactions are allowed. Termolecular reactions 
are not handled explicitly; a two-step mechanism must 
be employed.. There is no allowance for the input of 
equilibrium constants; reactions have to be entered 
separately in the forward and reverse reactions. The 
version used in this study is 1.4 (double precision), 
and handles up to 99 chemical species and 200 reactions 
(Braun et al., 1988). 
90 
This program was used to perform computer simula-
tions of electric discharge and o' - irradiated experi-
me n-Ls. In the case of electric discharges, the chemi-
cal change s occurring are poorly understand (Wiener and 
Burton, 1953; Kobayashi and Ponnamperuma, 1985b) . A 
p ossiLl e chemjcal model and its compu"Ler- modeling to 
a ccount for the observed chemical changes in electric 
discharge experiments will be described in Chapter 3. 
In contrast to electric discharges, the radiation 
chemistry of liquid water is one of the best understood 
doma ins of radiation chemistry (Draganic and Draganic, 
1971) . The reactions occurring during the irradiation 
of water are well known, and their rates of reactions 
have been determined by a variety of techniques (Buxton 
et al., 1988). 
Tables 2.3 to 2.7 summarize the system of chemical 
reactions used in this study to model the ~-irradiation 
of liquid water and aqueous solutions. Unless other-
wise stated, the rates of these reactions were taken 
from the comprehensive compilations of Anbar et al. 
(1971, 1975), Dorfman and Adams (1973), Ross (1975), 
Ross and Ross (1977), Buxton and Sellers (1978), Ross 
and Neta (1979, 1982), Hug (1981), Bielski et al. 
(1985), and Buxton et al. (1988). This set consists of 
91 
54 reactions . In section 2.8.1 two computer 
simulations are presented carried out with a well - un -
derstood irradiated system, the Fricke dosime ter, in 
orde r to demonstrate the validity of this set of reac-
tions . 
Table 2 . 3. Radiation and molecular product yields in 
irradiated liquid water by ~- rays and fast electrons 
with ene rgies in the range 0.1 to 20 Mev 1 ? 
No. Species G 
pH 0.46 pH 3 - 13 
1 - I-bO 4 . 45 4 . 10 
2 I-b 0.40 0.45 
3 fb(b 0.78 0.68 
4 H? 3.65 0.55 
5 HO? 2.90 2.72 
6 H. .. 0.00 2.65 
7 e..q 0.00 2.65 
1 . Draganic and Draganic, 1971; Spinks and Woods, 
1976; Buxton et al., 1988. 
92 
Table 2.4. Hydrogen atom reactions with transients 
from water. 
No . Reaction ki 
8 H- + H? fk 7. 8Xla9 
fkO 
9 H? + e..q Eb + Ho- 2.5x1010 
10 H? + - o- HO- 2.ox1010 
l l H? + HO? I-bO 7. 0Xla9 
12 H? + HO- e..q - + I-bO 2. 2Xl07 
13 H? -f I::bO I-b + HO? 1. ox101 
14 H? + I-beb I::bO + HO? 9. OX107 
15 H? + eb Heb? 2.1x1010 
16 H? + Heb? I-beb 1. ox1010 
1. The second order rate constant has units of dm3 
mole- 1 s - 1 . 
93 
Table 2.5. Hydrated electron reactions with transients 
from water. 
No. Reaction k1 
2H:z0 
17 8-q - + e-q Ek + 2HO- 5. 5X1
- CP' 18 e-q + w- H? 2_3x1010 
H:zO 
19 8-q - + - 0- 2HO- 2.2x1010 
20 8-q - + HO? HO
- - 3.ox10
10 
21 e-q + EkO H? + HO- 1. 9X101 
22 e-q - + (b -(b- 1. 9X1010 
EkO 
23 8-q - + - (k - 2HO- 1. 3X1010 
H:zO 
24 8-q - + Ha:z - HO? + 2HO- 3.5X1CP' 
25 8-q - + fk(b HO? + HO- 1.1x1010 
1. The second order rate constant has units of dm3 
mole- 1 s - 1 . 
94 
Table 2 . 6 . Hydroxyl radical reactions with transients 
from water. 
No. Reaction k1 
26 HO ? + HO? IkCk 5. 5X109 
27 HO? + . o- HCk - ~2.ox1010 
28 HO? + so- IkO + - 0- 1.3X1010 
29 HO ? + Ik IkO + H? 4. 2X10' 
30 HO? + HCk? IkO + Ck 6. OX109 
31 HO? + HCk - HO- + - Ck - + w- 7.5X109 
32 HO? + IkCk IkO + - Ck - +W 2. 7X10' 
33 HO? + IkCk ? .._ IkO + 02 + H.._ 1 . 2x101 0 
34 HO? + -~- HO- + Ck 8. OX109 
35 HO? + -(b - . Ck- + HCk? 8. 5X109 
1. The second order rate constant has units of dm3 
mole- 1 s- 1 ? 
Tabl e 2.7. Miscellaneous reactions with transients 
from water. 
No. Reaction k1 
EkO 
36 -o-? + -o- BCk - + HO- 8.3X109 
37 . 0- + w- HO? 1.ox1011 
38 ? O- + Ek H? + HO- 8. OX10' 
39 . 0- + EkO HO? + HO- 1. 8X1C>
40 -
6 
o- + HCk - HO- + . Ck - 4. OX10'3 
41 - 0- + EkCk EkO + -(k- ~5 . OX10'3 
95 
Table 2 . 7. Miscellaneous reactions with transients 
from wat er (Continue). 
No . Reaction k1 
4 2 . o- + Cb . Cb- 3. 6X109 
. o- EkO 4 3 + ? Q;_, -
44 . o-
Cb + 2HO- 6. 0X108 
+ -(h- (k + (k2- 8. 0X108 
45 -0:z- + w- Heb? 1.ox1011 
46 . 0::z - + I-bO Heb? + HO- 1. 0X109 
H::zO 
47 . 0:z - + H<k- I-b(k + (k + 2HO- 2.0 
48 . 0:z - + I-b<k HO- + HO? + (b 1. 3X10- 1 
49 HO:z. + HO::z? Ik<k + (k 3. 4X106 
50 Heb? + IkO::z HO? + (k + IkO 3.7 
51 a0:z - + IkO Ik<k + HO- 5. 0XlO7 
52 fk(b + HO- H<k- + IkO 1. ox1010 
53 H2O w- + HO- 2.5X1
54 H
0
_. -_ e + HO- IkO 1. 4X101 1 
1. The first and second order rate constants have 
units of s - 1 , and dn:r' mole- 1 s - 1 , respectively. 
2.8.1 Computer modeling of the Fricke dosimeter 
The Fricke dosimeter is a chemical system that is 
widely used to determine the dose rate of ionizing 
radiation sources (Draganic and Draganic, 1971; Spinks 
and Woods, 1976). The dosimeter measures the oxidation 
of ferrous sulfate solutions induced by the interaction 
of ionizing radiations. This chemical system is the 
most thoroughly studied in radiation chemistry and is 
96 
the basis for the wide use of the Fricke dosimeter. 
The standard system is composed of 10-3 mole dm- 3 FeSO... 
in air-saturated (2.5Xl0- 4 mole dm- 3 Cb) 0.4 mole dm- 3 
fkSO.,, (pH 0.46) (Spinks and Woods, 1976). The 
mechanism is well established, and the reactions 
involved are summarized in Table 2.8. 
Table 2.8. Relevant reactions in the Fricke dosimeter. 
No. Reaction k1 
Fl H + Fe2-+- HFe2 ... 7.5X106 
F2 HFe2-+- +W E-b + Fe3 ... 1. OXl<P 
F3 H + Fe3 ... Fe2 ... + w 6. OX106 
F4 HO+ Fe2 ... Fe3 ... + HO- 1. 7X10'9 
F5 H~ + Fe2 ... Fe3 ... + HCb - 2. 5X106 
F6 H:z~ + Fe2 ... Fe3 ... + HO? + HO- 6.2X102 
F7 Fe3 ... + e.q- Fe2 ... s.ox1010 
1. The second order rate constant has units of dm3 
mole- 1 s- 1 . 
The computer modeling of this system consisted of 
the chemical equations summarized in Tables 2.4 to 2.8, 
and the radiation chemical yields of primary species 
from water at pH 0.46 (Table 2.3). Figures 2.10 and 
2.11 show the computer modeling of the Fricke dosimeter 
97 
?0  
X: 
..., 2 .0 
I 
F 
'U 
0 
E 1.0 
..._, 
,......., 
+ 
P'") 
L"L  0.0 '-' 0 10 20 30 40 50 
llme ( 8 ) 
Figure 2.10 . Computer Simulation (solid line) 
F or fi  c tk he e  Dosimeter after a 155 Gy electron pulse. 
tio Cn os n: d i1 -0- 3 mole dm- 3 FeS~ in aerated (2.4X10- 4 
dm -3 
mole 
0:::,,) 0.4 mole dm- 3 fkS~. Experiment.al dat
w a as ( 0t )a  ken from Rasmussen and Bjergbakke, 1984. 
under various conditions. 
The excellent computer fitting with the experimen-
tal data shown in Figures 2.10 and 2.11 demonstrates 
that the chemical equations included in the data base 
(Tables 2.4 to 2.7) can effectively model the radiation 
chemistry of liquid water. Such a good agreement 
between experimental and computed trends is not 
surprising since the mechanism of water radiolysis has 
been thoroughly investigated and is one of the domains 
of radiation chemistry best understood (Draganic and 
Draganic, 1971). The development of pulse radiolysis 
techniques contributed significantly to the determina-
98 
16 
- .... ,+.,  12 ~ '\, 
L"o.. ' \ .........  \ 
0 \ 
B 
\ 
' 
\oi ,o-1 104 10!! 106 1()7 
Dose rate ( kGy ? s- 1 ) 
Figure 2.11 . Computer Simulations (line s) of the 
Effect of G (Fe 3 - ) on Dose Rate after a 1 u sec electron 
p u l se. Conditions: 10--3 mole dm- 3 FeSO.. in aerated 
{ 2. 4X10- 4 mo l e dm- 3 Oz) 0. 4 mole dm- 3 Ik SO.. ( v , 
- - - ); 10--2 mole dm- 3 FeSO.. in oxygenated {1.2X10-- 3 
mol e dm- 3 Oz) 0.4 mole dm- 3 IkSO.. ( 0, --- ) . 
Experimental data (v ,O) were taken from Thomas and 
Hart , 1962 . 
ti on of very accurate rate constants of unstable 
spec ies produced in liquid water (Buxton et al., 1988). 
2.9 Presentation of data 
The experimental data were fitted by polynomial 
reg r ession analysis to show the trends of data points . 
No conclusions as regards to reaction mechanisms were 
drawn f r om the mathematical equations used in the curve 
fi tt i ng . 
99 
CHAPTER 3 
RE: 
ELECTROLYSIS OF A SIMULA
TED PRIMITIVE ATMOSPHE
E 
THE SYNTHESIS OF HYDROGE
N CYANID
3.1. Introduction 
n production of HCN 
The electric discharg
e drive
ported in numerous st
udies in prebiotic 
has b een re
t al., 1966; Pon-
chemistry (Miller, 1
957a; Sanchez e
975; 
eruma et al., 1969; Y
uasa and Ishigami, 1
namp
 1975; Kobayashi and
 Ponnamperuma, 
Toupance et al.,
le or 
19 ribling and Miller, 1
987). However, litt
85b; St
e measurement of the iven to th
no attention has bee
n g
t dif-
eld . This is due in 
part to the apparen
HCN Yi
mining the amount of
 energy transferred 
ficulty of deter
systems . 
the electric discharg
e to the absorbing 
from 
her products 
Consequently, the yi
elds of HCN and ot
f h percen-
t,, . ally have been express
ed in terms o t e 
JPlc
s converted into 
tage of the initial 
carbon atom
; Kobayashi and 
Products (carbon yie
lds) (Miller, 1974
100 
Ponnamperuma, 1985b, 1986; Stribling and Miller, 1987). 
A method of directly determining the energy intro-
duced (E~) by electric discharges has long been recog-
nized {Wiener and Burton, 1953), in which E~=IVt/n, 
whe re I and V are the discharge current and voltage, 
respectively, t 1s the reaction time, and n is the 
number of moles of T hg ea  s m. easurement of such 
variables have been reported in some prebiotic experi -
ments carried out in this laboratory (Ponnamperuma et 
al . , 1969; Park et al., 1975} and in others (Toupance 
et al., 1975; Harada and Iwasaki, 1975; Harada et al., ? ' 
I 
l978, 1984; Terasawa and Harada, 1980). 
Measurement of the electric quantities {e.g. 
voltage, current) of prebiotic discharge experiments is 
cti? fficult because they are most frequently done at 
high voltages{> 20,000 volt) at high frequencies 
(> 0.5 MHz}. Voltage measurements in spark discharges 
~ere previously reported from this laboratory using a 
high voltage attenuator probe coupled to an 
In a different 
o as pc -illoscope (Park et al., 1975). 
Proach, the energy input was estimated by measuring the 
input voltage and current supplied to a Tesla coil 
(Shimoyama et al., 1978). The energy determined by 
this last method includes, however, the energy intro-
101 
duced into the system not only as spark discharge but 
also the electricity converted into heat in the trans-
former. 
A different method has been recently reported in 
which the energy introduced into the system was estima-
ted by comparing the heat evolved during the sparking 
of an insulated discharge system with that produced by 
a known power input across a resistor (Stribling and 
Miller, 1986, 1987). However, the authors in that 
study did not take into account the energy converted 
into chemical form, light, or that not absorbed by the 
gaseous system. Navarro-Gonzalez et al. (1986) have 
calculated that up to 24% of the energy introduced by 
the electric discharge can be converted into chemical 
form. In addition, gases have a low collisional mass 
stopping power when they are irradiated with low energy 
electrons (Spinks and Woods, 1976) such as are produced 
by electric discharges. As a consequence the method of 
Stribling and Miller underestimates the amount of ener-
gy intrcxluced by electric discharges. 
The purpose of this study is to develop dosimetric 
methcxls for high voltage, high frequency electric dis-
determ
ch inar eg  e ths e raa dn iatio o na ately  , d t ccur 
chemical yield (G) of HCN in the electrolysis of a 4.2 
102 
dm3 gaseous mixture at 60?C and 600 Torr composed of 
0.0108 mole dm3 of methane, 0.0108 mole dm- 3 of 
nitroge n, and 0.00782 mole dm- 3 of water vapor in equi -
librium with a liquid phase of 0.1 dm3 of 0.05 mole 
dm- 3 aqueous ammonium chloride buffer at pH 8.7. 
Three different methods were successfully applied 
to determine the dose supplied by electric discharges. 
The methodology is described in Chapter 2, section 
2.4.1, and the results are reported here, in section 
3.2 . Once an accurate knowledge of the dose introduced 
inLo the electric discharges experiments was concluded, 
we could measure the initial chemical yields (G 0 ) of 
HCN and other early products from the electrolysis of a 
CH,.q.-tb - fkO mixture. The results and a discussion are 
given in section 3.3.1. A mechanism to explain the 
electrolysis of the CH....-tb-EbO mixture, and the forma -
tion of HCN is given in section 3.3.2. The implica-
tions of this study to chemical evolution are given in 
section 3.3.3 and the conclusions in section 3.4. 
3.2. Dosimetry of high voltage electric discharges 
The dosimetry of electric discharges was performed 
by chemical dosimetry, and electric and calorimetric 
103 
ts of discharge voltage and
 current. The 
measuremen
easurements are given below
. 
results from these m
3.2.1 Chemical dosimetry 
ethod 
The chemical dosimeter is 
an indirect m
r and dose rate supplied 
developed to estimate the 
powe
ctric discharges using the
 
by alternating current ele
chemical system investigat
ed by Wiener and Burton 
ethane at 25?C and 760 Torr
. 
(1953) : gaseous m
alysis of the data reported
 by Wiener and Burton 
An
) on the direct current el
ectric discharge of 
(1953
thane at atmospheric press
ure indicated that the 
me
ulated 
Power (P) of the electric 
discharge could be calc
on 2.4.1, 
according to the following
 equation (see Secti
Pages 65 - 68): 
1.6022X10-
1
' k(-Cfk) 
p -
G O (-CU..) 
ction of methane in 
~here, k(-CH ) is the rate 
of destru
4
104 
0 
e electric discharge; and G ( -
CH..i.) is the initial 
th
 of methane. 
chem ica l yield of decomposition
 of 
Calculating P required an accu
rate knowledge
O O 
G - CH4} . G (-CH-i.) was not 
determined by Wiener and 
( 
alculated from their 
Burton (1953), and therefore, w
as c
data for this study (see pages 
65- 68, this disserta-
O .,.) with 
tion}; a value of 8. 34 was deri
ved for G (-CH
an error of 20% (see Figure 2.3
). 
ane was determined 
The rate of destruction of meth
in the alternating current elec
tric discharge of 
) 
methane at atmospheric pressure
 (Figure 3.1); k(-C~
N 
N 
I 1.00 
.0.. . 
X 
.---. 0 .76 
l'l 
I) 
"a 0.60 
..&"..I   
a0 ....,  0.20 
..,. 
::r:: 0.00 
u 0 3000 600
0 9000 
I 
Time (sec) 
ime dependence of the destructi~
n of 
Figure 3.1. T
ane in the alternating current 
electric discharge 
meth
of methane at 25?C and 760 Tor
r. 
105 
was calculated from the slope of the curve shown figure 
3 . 1 by linear regression analysis, and was determined 
to be : 8.73X1017 molecules sec- 1 with a correlation 
coefficient of 0.986. The standard error of the data 
was calculated to be within 6%. 
The power of the electric discharge was, therefore 
determined to be 1.68 W, with an estimated error of 
20%. The error is mainly due to the deviation in 
G O ( - CH ... ) . 
The dose rate (Gy s- 1 ) of the electric discharge 
experiments was calculated from the equation, 
Dose rate P I m 
where, Pis the discharge power; and mis the number of 
kilograms of gas in the electric discharge system, and 
is 2.65Xl0- 3 kgr for our CH...-~-IkO system. The dose 
rate is, therefore, 634 Gy s - 1 , or 2.28 MGy hr- 1 ? 
This method was the first dosimetric technique 
that was developed. Initially, the values of power and 
dose rate of the electric discharges were considered 
as estimates since we did not know if these parameters 
depended on the composition of the gas phase. Subse-
106 
quently, two additional methods were developed (Sec-
tions 2.2.2 and 2.2.3), and it was found that these 
parameters do not depend on the chemical composition of 
the system. Furthermore, the dose rates determined 
independently by the different methods agreed to within 
a 15% deviation (Section 3.2.4). 
The chemical dosimetric method described in this 
section was simple and reproducible. The determination 
of power and dose rate was obtained in a matter of 
hours for a single assay: this includes sample prepara-
tion, irradiation, and analysis. Several samples must 
be analyzed at various time intervals in order to 
obtain an accurate determination. The only precaution 
that must be taken into account is to measure the 
amount of methane decomposed when its rate of destruc-
tion is linearly related with irradiation time; this is 
usually at methane conversions ~50% (Figure 3.1). 
3.2.2 Electric measurements of voltage and current 
Asymmetrical sinusoidal signals with a frequency 
of 0.3 MHz were produced for both discharge voltage and 
current (Figure 3.2). This frequency was independent 
of the chemical composition and conditions of the 
107 
60 
-> ~ 50 
Ill 
.Isl l 
~ 0 
wIll  
j - 30 
CJ 
!! 
A - 60 
0 5 10 15 mo 
....... 1.0 
.: 
........ b 
... O.t'> 
f 
~ 0.0 
Ill 
~"?  -0.6 
.cl 
() 
I? 
iS -1.0 
0 6 10 16 190 
Time (?sec) 
Figure 3.2. Peak- to- Peak and Zero-cro
ta ssk ie nn g  1 Vro am lu et sh  e Oscilloscope were plott
c eu dr  v be y  f si mtt oi on thg   to obtain the Voltage (a
O ) s ac ni dll  a Cti uo rrn es n tp  r (o bd )u  ced by an Electric Disc
a ht a rgro eo  m in  te Am irp  erature and atmospheric pr
g ea sp s) u. r e (1 cm 
system. The discharge voltage and current collapsed 
in about 10 wsec, and re-generated in about 190 ?sec. 
A cluster of about 14 electric discharges were produced 
every 7.2 msec; the average frequency was calculated to 
108 
be 514 wsec per electric discharge. 
The total voltage and current {Y) supplied by the 
electric discharge were calculated according to the 
following expression, 
n 
A { ::::: X.,,.i ) 
i =l 
y -
F 
whe r e , X.:C, is the absolute peak value of each positive 
and negative components during a transient discharge 
occurring in an interval of 10 wsec; A= 0.637, and is 
a conversion factor to calculate the area of a sinusoi -
dal signal from its peak values{~) (Malmstadt et al., 
1981); and F = 514 wsec, and is the frequency of elec-
tric discharge. 
The total voltage was found to depend under cer-
tain circumstances on the resistors (R) used to measure 
this quantity. Figure 3.3 shows the dependance of 
voltage on the total resistance of R1 and R:z. At low 
---------------------------------------------
109 
15()0 
,,...... 
-> ( Rt + R2) 1000 -QI ..I.I.  f 
~ 5()0 
0 
5 10 15 20 
Resistance (MO) 
Figure 3.3. The Effect of Resistance of Ri + 1k on the 
Voltage of a 1 cm gap Electric Discharge in Air. 
total resistance for Ri and lk, the voltage increased 
up to about 3M ~ , where it reached a steady value of 
about 470 V (Figure 3.3). This effect was attributed 
to the facility by which electricity could flow more 
freely through the pathway containing Ri and Rz as the 
resistance on this pathway decreases {see Figure 3.4 
for the electric circuit): Wben the resistance on such 
a pathway was zero, electric discharges were no longer 
produced. 
110 
TC 
CM VM 
DM 
AC 
=G 
Figure 3 . 4. Schematic Representation of Electric Cir-
cui~s for Measuring the Discharge Voltage and Current. 
AC: Alternating current power; CM: Current me asureme
D nC t: ;  Discharge chamber; DM: Digital multimeter; G: 
Ground; R : Resistors; TC: Tesla coil; VM : Voltage 
measurement. 20.0~RiL0.5 M u ; 10.0~lkL2.0 k Q; 
1000~R"32. 50 ~1. 
The voltage measurements for dosimetry of the 
electric discharges were taken at high resistance for 
R, and Rz, usually above 5 Mu , in order to minimiz e 
any interference on the electric discharge. 
The current of the electric discharge was not 
altered by the resistance used for lh. This is demons -
trated in figure 3.5 where the current is plotted 
against a wide resistance range from 50 to 1000 u for 
111 
0 .009 
........ R3 
ct 
........ 0 .006 
...... 0 (.) 
~ 0 0 '9 
..
C.I.I  0 0 .. 
:: 0, .003 0 
u 
0.000 
0 250 600 750 1000 
Ri::iehilll!lnce ( 0) 
F igure 3.5 . Th e Effect of Resistance 
r oen ft ~ o  of n a th1 e cm C ug ra -p Electric Discharge in Air. 
Electric discharge experiments were performed at a 
1 c m dis c harge gap; however, in order to gain insight 
on -Lb e effe ct of discharge gap size on voltage and 
current, we studied the electric quantities {e.g., vol -
tage , curre n t ) as a function of discharge gap size. 
The total voltage increased linearly with the length of 
the discharge gap. Figure 3 . 6a shows this effect from 
0 to 1 cm discharge gap; at high discharge gaps {23 
cm) , electric discharges were no longer produced. 
The total current of the electric discharge also 
increased linearly with the length of the discharge 
gap . This effect is shown in Figure 3.6b . 
112 
600 
a 
,..,. 
.>..., . 
.t,i  260 
~ 
0 
> ? ' 
0.4 O.B 1.2 
B.O 
~....  b 
I>< 
~ 
......... 4 .0 
.... 
A 
f 
~ 
u 
0.0 
0.0 DA 0.8 1.2 
Di?charge Gap (cm) 
Figure 3.6. Dependence of 
( thb) e  w Voit lh ta gth e e ( aE )l  e ac nt dr  i Cc uD rri es nch t 
p ao rgse ed  g ao pf   iA ni  r a  a st y sA tet mm  o cs op mhe -ric Pressure. 
The pressure dependence of voltage and current 
was studied in different gaseous systems: air, CH4, and 
The electric discharges were produced with 
different Tesla coils and using different outputs. 
The experiments were performed at various discharge 
gaps from 0 . 1 to 1 cm. In order to normalize the data, 
the voltage and current per gap length were plotted 
113 
v ersus pressu r e (Figure 3 . 7) . The voltage per g ap 
length linearly i n c r e a sed with the tot.a l p ressu re of 
1~ ,----------------, 
?. ? , A X 10- 3 A. c:m- 1 b 
._ X 10-? 
10 
t 
-? - ?- ?- - ? .- ?- ?-?- __. . _ -?-?-?- ?-?- ?- ?- ?- ?- ? 
..... 6 ? a ? ? 
j - -i - -~ - - - - _. . _ - "- - -- - - -,-? 
0 .___ __ ,__ __, ___ __ .__ __ _, 
o 200 .oo eoo eoo 
Pre111ru re ( 'l'orT' ) 
F igure 3. 7. Pressure Dependence of V
C ou lr tr ae gn e t (a(L ) ) anp de  r Discharge Gap Lengt
c ho . i l N::z/0:z =m 3( o .A d  7) , e l   TB eD s- l5 a0  , Output 8, disc
e hx ac re gp et  ga at p =7 06 .0 7  T co mr , r, where it varied 
{ fr? o m)   ; 0 .C  1l-  k t, o  D 1i .s  0c  h ca mr  ge Gap=0. 7 cm, T
B eD s- la5  0 c, oo ilu  t (p Bu )t   m4 o. d5 e l(   I! ); N::z/CH.,.=1, D
Te is scla h arc go ei  l g am po =d l el c mB ,D  - 50E, output 5.6 
co { i &l   ) and{A) m  o Td ee sl l aB  D- 50, output 8 { L ). 
114 
the system and did not depend neither on the h . 
c em1ca1
c  omposition of the system nor on the instrum t 
en used 
produce the electric discha tr og  e (Figure 3 . 7a). The 
current per gap did not depend strongly on the 
total 
pressure of the system but did depend on b th 
0 the Te s 1 a 
coil and the output used (Figure 3.7b). Tl 
ue minimum 
pressure plotted in Figure 3.7 corresponds to 
1 T orr; 
however at lower pressures (~50 mTorr), electric dis -
charges were no longer produced. 
The measurement of discharge currents and 
voltages 
was carried out in a matter of minutes and was Per-
formed routinely for each experiment. During low vol -
tage and current measurements a noisy baseline was 
obtained on the oscilloscope due to reception of radio 
waves (around 5 MHz) produced by Tesla coils. These 
radio waves were visible on the oscilloscope even with-
out direct connection to the electric circuit. In 
order to eliminate the effect of noisy baselines, the 
determinations of voltage and current were obtained 
with a number of resistances for Resistors 1 to 3. R
1 
was usually varied from 3 to 20 M Q ; 1k was changed 
from 2 to 10 k Q; and~ was modified from 0.05 to 1 
k Q _ The standard deviation from all of these dif-
ferent sets of measurements was determined to be 12%. 
115 
The power of the electric discharge was calculated 
by the equation, P =VI; where V and I are the total 
voltaae and current of the electric discharge, respec-
tively. Its value depended on the discharge gap length 
and the total pressure of the system and ranged from 
0.01 to 2.29 W. The power of the electric discharge 
did not depend on the chemical composition of the sys -
t e m. 
From the above studies, we conclude that the power 
of the electric discharge delivered in the electrolysis 
of the CB.. . - N:z - fkO mixture was 2.29 W with a deviation 
of 0.27 Wat 60?C, 600- 160 Torr, and at 1 cm discharge 
gap length. The dose rate was calculated to be 864 G 
s - 1 or 3.11 MGy hr- 1 ? The standard deviation was 
deLermined to be within 12%. 
3.2.3 Calorimetric measurements of voltage and current 
The values of voltage and current were derived 
from the measurement of the heat dissipated from resis -
tors 1 and 2 in an insulator box during the sparking of 
the electric discharge experiment (see Figure 2.5 for 
the experimental diagram). Figure 3.8 shows a typical 
experiment in which the rise of temperature was 
116 
- 28 u 
0 
........ 
Ql 
~ 
-+-> Z6 
~ 
"Q"l 
s0-
 .  
II) 
E-< u 
0 2000 4-000 6000 6000 
Time ( sec ) 
Figure 3.8 . Temperature Increase as a Function of Time 
during the Calorimetric measurement of Voltage ( 0 ), I l' 
and Voltage and Current { 6 ) of the Electr ,,i  c Discharge 
of Air at 760 Torr and 1 cm discharge gap. 
Ri=0.5 M Q ; lk =5 k D ; { 0) Qi=1.16X10- 4 ?C sec- 1 ; 
( L. ) Q1 .... 2 =8.87X10- 4 ?C sec- 1 ; C:,=1594.4 W sec 0 C- 1 . 
measured as a function of time for voltage and both 
voltage and current of the electric discharge. The 
heat (Q) dissipated from Ri and R1+lk was calculated 
from the slopes (m) of the curves (Figure 3 . 8) and from 
the heat capacity (Cp) of the calorimeter: Q = Cp m. 
The beat released by R1 was unmeasurable at 
resistances of 21 M 2 , and only resistances of ~0.5 M 2 
could be used to accurately determine the beat dis -
sipated . The voltage of the electric discharge was 
117 
determined using resistors from 0.5 M Q to 0.02 M 2 
without affecting its value. In the previous section, 
it wa s sh own that at low resistances for R1 and Ik, the 
voltage of the electric discharge is diminished {Figure 
3.3), and consequently less current flows through the 
e l ectric discharge pathway and more through that 
containing R1 and lk. In spite of this alteration, the 
total amount of electricity that flows in both pathways 
was constant {see Figure 2.5 for the electric diagram). 
This conclusion was reached after determining that the 
t ota l consumption o-f e]ectricity by the Tesla coil was 
unaffected by connecting R1 and lk to the electric 
,. 
discharge. Be cause of this I  effect, the voltage and '., 
current we re simultaneously determined by measuring the 
heat dissipated by R1 and lk in order to quantify the 
total amount of electricity that flow in both pathways. 
Independently, the voltage was also measured to be abl e 
to solve for the value of current from the previous 
determination . The resistance of 1k was adjusted to 5 
k Q and was not varied since the current of the elec-
tric discharge was not interfered by the value used for 
Ik {see Figure 3.5). 
The power of the electric discharge experiments 
was determined to be 2.07 Wat 60?C, 600-760 Torr, and 
an 1 cm discharge gap length. It was found to indepen-
118 
d ent of the chemical composition of the system use d. 
The dos e rate was d e termined to be 781 Gy s - 1 or 2.81 
Th e standard d e v i ation was calculated to be 
26% . 
Th e d os ime Lry of an electric di sct1arge experiment 
by t h i s method was simple and could be accomplished in 
a relatively short period of time, about 6 hrs. The 
only inconvenience was to determine the appropriate 
resistance of R1 in order to obtain a measurable beat 
dissipat ion rate; this was about ~0.5 M ~ at 1 cm dis -
charge gap and 760 Torr of total pressure for the sys -
,? 
tem. :,I  
' 
3.2.4 Comparison of the different methods 
The three methods described above (sections 3.2.1 
to 3.2.3) were effective in determining the dose rates 
of the electric discharge experiments. The dose rate 
vary from 2.28 MGy hr- 1 (using the chemical dosimeter) 
to 2 . 81 MGy hr- 1 (calorimetric measurements of V and I) 
or 3.11 MGy hr- 1 (electric measurements of V and I), 
and in all cases was independent of the chemical com-
position of the system. The average dose rate was 
determined to be 2.73 MGy hr- 1 ? The standard deviation 
119 
among the three different methods was reasonable, 15% . 
This value is to b e contrasted to a 50% deviation ob-
taine d by Stribling and Miller (1987) using a different 
approac.;h to determine the energy introduced by electric 
discharges. 
The method suggested by Stribling and Miller 
(1987 ) consists of determining the power of the elec-
tric discharge by measuring the heat evolved during the 
s parking of the electric discharge sample (Stribling 
and Miller, 1987) . We have already discussed that this 
approach underestimates the amount of energy supplied 
by the electric discharge since it does not taken into 
account the energy converted into chemical form, light 
and that not absorbed (see section 1.2.3). In order 
to experimentally demonstrate the weakness of such a 
meth od, we also determined the power in our electric 
discharge experiments according to their method (see 
page 72 for experimental conditions). 
Figure 3.9 shows the temperature increase as a 
function of time during the sparking of an electric 
discharge experiment. The power (P) of the electric 
discharge was calculated from the slope of the curve 
(m) and the heat capacity of the calorimeter (Cp): 
P = Cp m. The average value of P was 0.37 W with a 
120 
26 
26 
24 ----~----,c-----------j 
0 2000 4000 
Figure 3.9. Temperature Increase as a Function of Time 
during the Measurement of Power of a 1 cm Electric 
Discharge in air at 760 Torr. m=4.89Xl0- 4 ?C sec- 1 ; 
C.C. =1594 . 4 w sec 0 c- 1 ? 
standard deviation of 10%. The dose rate was deter-
mine d to be 140 Gy s - 1 or 0.50 MGy hr- 1 ? Therefore, 
the method of Stribling and Miller underestimates the 
dose rate by about a factor of 5. 
3.3.4 Evaluation of the dosimetry of electric 
discharges 
Electric discharges have been extensively used to 
induce abiotic syntheses in the last forty years (see 
for instance, Fox and Dose, 1977). The measurement of 
the amount of energy supplied from the electric dis -
121 
charges ha s b een usually neglected mainly bec aus e of 
the difficulty of d etermini ng such a parameter , and 
only r ecently h a v e there b een atte mpts to estimate this 
quani ,ity by Navarro- Gonz.:i lez et al . (1986 ) and Stri -
bling and Mi ller (1986, 1987). Howeve r, this is the 
rirsL study 1n whi ch the dose rate of abioti c discharge 
expe riments is comprehensively investigated . 
Th e average dose rate of our electric discharge 
experiments was determined to b e 2.73 MGy hr- 1 at a 1 
cm gap electric discharge and 600 Torr of pressure . 
This value depends on the discharge gap lengLh and the 
total pressure but does not depend on the chemical com-
position of the system. 
Knowledge of the dose rate of electric discharge 
experiments is important because it allows to determine 
the dos e absorbed in the experiments and to calculate 
the chemical yields of the products. Furthermore, it 
p e rmits direct comparison with other energy sources in 
order to contrast the relative contributions that they 
may have played in the syntheses of organic compounds 
in the primitive Earth. The next sections on this 
chapter demonstrate the accomplishments that are ob-
tained by knowing the dose rate of electric discharge 
experiments. 
122 
3.3 Electrolysis of gas mixture 
The electrolysis of a 4 . 2 dm3 gaseous mixture at 
60?C and 600 Torr composed of 0.0108 mole dm3 of 
methane , 0.0108 mole dm- 3 of nitrogen, and 0.00782 mole 
dm- 3 of water vapor in equilibrium with a liquid phase 
of 0.1 dm3 of 0.5 mole dm- 3 aqueous ammonium chloride 
buffe r at pH 8.7, was investigated in the dose range 
from 0.38 to 152.30 MGy. 
3.3.1 General 
Qecomposition of initial......ru!ses. Methane and nitrogen 
were identified and quantified in the electrolyzed 
samples and blanks by mass spectrometry. Figure 3.10 
shows the decomposition of methane as a function of 
dose. The concentration1 of methane linearly decreased 
with dose up to about 20 MGy and then decreased 
steadily up to about 150 MGy; less than 6% of the 1n1-
tial methane remained in the dose range from 80 to 150 
1 The concentrations of solutes and/or prcxlucts are 
given in terms of moles per dm- 3 of gas phase. 
123 
- 0.012 "f'  
E 
'"O 
0.008 
? 
0 
E 
-...., 0.00-4 ? 
,......., 
-.t 
:r: 
,_l_),  ? 0.000 
D -40 80 120 160 
Dose ( MGy) 
Fig ure 3 . 10 . Dose De pendance of the Dec ompos ition of 
Me t h ane in the Hig h Vo ltage Electric Discharge o f CH4 -
N2 - fk O . 
MGy. The initial che mical yield2 (G 0 ) of the d ecom-
posit ion of methane was determined to be: 
G O ( - Cll4 ) =6 . 5 4 . 
Th e d ecomposition of nitrogen as a function of 
dos e i s shown in Figure 3.11. The concentration of 
nitrog e n linearly decreased with incre asing dose up to 
about 40 MGy, where it reached a steady value of about 
0.0081 mole dm- 3 in the dose range from 40 to 150 MGy . 
Th e chemical yield of decomposition of nitrogen wa s 
2 The chemical yield (G 0 ), number of molecules formed or 
destroyed per 100 eV absorbed, is calculated from the 
slope of a dose versus dose curve, e.g. as Figure 
3 . 10. 
124 
r;") 0 .0 12 
I 
8 
"O 
..C...l).  
s0  
,......., 
N 
:7. 0 .006 +-- --~--- ~--~----a 
'--' 0 20 40 60 80 
Dase ( MGy) 
Fi~ure 3 . 11 . Dose De pendance of th e Decomposition of 
Nitro{;en in the High Voltage Electric Discharge of 
en,. - N2 - fh. o. 
d e t e rmj ned t o b e: G O ( - ~) 1.26. 
Nitro~en was quite stable to electrolysis; its 
decompos ition occurred only in the dos e range where a 
significant amount of the original methane remained in 
the system down to about 20% of CH4. This suggests 
that the channel of decomposition of nitrogen depends 
on methane and/or a transient che mical species formed 
in the decomposition of methane during the bombardment 
of electrons into the system. 
Formation of hydrogen cyanide . HCN was identified and 
quantified by its titration with silver nitrate and 
125 
wi t h a s e lective cyanide electrode . Its concentration 
increased linearly at l ow dose and then steadily above 
30 MGy (Figure 3 . 12); its chemical yi e ld of formation 
wa s d e termined to b e : G 0 (HCN) =0.26. About 10% of the 
initial me Lhane or nitro~t!O wa s converted into HCN at 
150 KGy. 
t') 
0 
-' 1.2 
X 
........ 0 
(") 
I 0.8 
~ 
Q) 
0s  0.4 
.__., 
,....., 
zu  0.0 
.:.:.r.:. . 0 60 100 150 
DoBe ( UGy ) 
Figure 3.12. The Effect of Dose on the Synthesis of 
Hydrogen Cyanide in the Electric Discharge of CH,. - N:2 -
fbO . 
In order to get a better insight into the chemical 
mechanism of formation of HCN during the electrolysis 
of the simulated atmosphere, other initial products 
126 
such as hydrocarbons and aldehydes were also -
investi -
gate d . 
1''ormation of ___bygroca~bons. (b fb and (b Ho were 
identified and quantified in the experiments by 
mass 
spectrometry; however, (bfk could not be quantified 
because its molecular ion (C2H4+, 28) and the Pre-
dominant fragment (C2H3+, 27) formed in the mass spec-
trometry analysis overlapped with those of ethane and 
also nitrogen (ttz+, 28); the latter were extremely 
abundant. 
Figure 3.13 shows the formation of (bfb and ?tk 
as a function of dose. At low doses, their concentra-
tions linearly increased with dose up to a maximum 
located at about 30 MGy; these maxima also coincided 
with the maximum decomposition of methane (Figure 
3. 10). C2fb was the most abundant hydrocarbon, and its 
chemical yield of formation was determined to be: 
G D ( C2 H:z ) =2 . 14 . C:zHo was formed with a smaller chemi-
cal yield: G 0 (C2Ho)= 0.57. The concentrations of C:zlk 
and C2Ho decreased rapidly with increasing dose start-
ing after about 50 MGy. 
127 
~ 
2.0 2.0 1 I"; 
I'll 
.., 
I 1.6 n 1.6 I 
~ ~ 
? 1.0 'o 1.0 .. ,; 
..f.l. , a 
0.6 
? 
Oi 'i 
.l..)...  0.0 
60 ..
~.....  
0  100 160 
? 
Doee ( WGy} 
Figure 3 . 13 . The Effect of Dose on the Formation of 
C2H:z and C:zI:k, in the High Voltage Electric Discharge of 
CH,. - N2 - Ik O. 
Formation ol aldehydes. Figures 3.14 and 3.15 show a 
gas-chromatogram and mass spectra, respectively, of 
aldehyde products that were derivatized via 2,4- dini -
trophenyl-hydrazine (DNP) into 2,4-dinitrophenyl-
hydrazones (DNPH) derivatives. Acetaldehyde, 
propionaldehyde and butyraldehyde were identified by 
gas chromatography based on their retention times and 
coinjections with standard DNPH derivatives; additional 
evidence was provided by detection of the mass ions and 
the mass ions plus one in the electron impact and 
chemical ionization mass spectrometric analyses, 
respectively (see Figure 3.15). 
128 
1 
Q) 
rtJ 
A 
0 
p, 
(I) 
Cl,) 
n:: 
2 3 
0 5 10 
Time (min) 
Figure 3.14. Gas Chromatogram of DNPH Derivatives of 
Aldehydes Formed at 6.35 MGy. 1. Solvent (ClbCb); 2. 
DNP; 3. Formaldehyde; 4. Acetaldehyde; 5. Propional -
dehyde; 6. butyraldehyde; 7 and 8. Unknowns. 4' and 6' 
are syn isomers. 
A peak (3) in the gas chromatographic analysis of 
DNPH derivatives at high doses, 21.59 MGy, (Figure 
3.14) was resolved with a retention time corresponding 
to that of formaldehyde; coinjection of the electric 
discharge sample with a standard solution of formal-
dehyde- DNPH resulted in an increment of the area under 
peak 3. The electron impact mass spectrum of this 
fraction (Figure 3.15a) demonstrated the presence of a 
low abundance, ~ 1%, mass fragment, 210 m/e, that could 
originate from formaldehyde-DNPH (M.W. 210); however, 
the mass ion plus one was not produced by chemical 
ionization mass spectrometry under similar conditions 
129 
100 
122 
5 0 
152 
1EIO 262 
131 
~ 
lt'i 
w 
0.. 0 50 100 150 200 250 300 
Q) 
r.a 
~ 
lil 
..... 
b 225 0 100 
~ 
50 
122 l&i 206 
0 
60 100 160 200 250 300 
m/e 
Figure 3.15. Mass Spectra of DNPH Derivatives Formed 
at 1.59 MGy . Electron impact mass spectrum (a). Mass 
ions: Acetaldehyde (224); propionaldehyde (238), and 
hutyraldehyde (252). Chemi ca l ionization mass spectrum 
(b). Mass ions plus one: Acetaldehyde (225), propion-
aldehy<le (2 39 ) , and butyralde hyde (253). 
(Figu r e 3.15b). The identification of formaldehyde is, 
therefore tentative at the present time; further work 
needs to b e done at high doses in order t o obtain a 
higher amount of sample for its analysis and subsequent 
130 
identification. The concentration of formaldehyde was 
esti mated to Le ~1.05X10-- 6 mo le dm- 3 at 6 . 35 MGy; the 
d e rived chemical yield was calculated to be: G" (HCI-10)~ 
0.00264. 
Other peaks (7, and 8) in the gas chromatographi c 
analysis of DNPH d erivatives we re not id e ntified 
(Fiaure 3 . 14). Th e y we re only prese nt at the highest 
dose (6 .35 MGy) analyz e d for this type of compounds. 
Figure 3.16 shows the formation of acetaldehyde, 
propionaldehyde, and butyraldehyde as a function of 
dose. Their concentrations increased linearly with 
dos e up to about 1.6 MGy, and then reached a ste ady 
value (for propionaldehyde) or decreased (for acetal-
dehyde and butyraldehyde). Their chemical yields were 
determ i ned to be: G O ( Cfb CHO) =O. 13; G O ( CI-h CEb CHO) = 
0. 011; and G 0 (CfbCEbCEbCHO) =O. 016. 
131 
cc 
0 
..-1 
>< 9.0 
........ 
.
t ai' .)   X 10 
I 
~ 6.0 
DX5 
..C...l.)  
0 
-s s.o ,....., 
0 
:u:c  0.0 
~ 0.0 . 2__ ., 0  4.0 6.0 
Dose ( M:Gy) 
Figure 3.16. Dose Dependance of the Formation of Alde-
hydes in the Electric Discharge of Cfk - ~-EkO: Acetal-
dehyde ( 0 ); Propionaldehyde ( L ); and butyraldehyde 
( D ) . 
Formation of oligomeric material. A water-insoluble 
material deposited on the walls of the flask during the 
elec trolysis of the gas sample. The material was 
analyzed for H, C, and N content in order to evaluate 
its yield of formation and to perform a material 
balance of major products from the electric discharge 
experiments. Figure 3.17 shows the formation of such a 
material as a function of dose. Its abundance linearly 
increased with dose; its rate of formation was 
calculated to be 2.12x10- 2 gr dm- 3 MGy 1 , and was 
132 
M 
I 0.06 
El 
'O 
a.. 
1111 
....... 0.04 0 0 
r...-...,  
<11 
-~ 
cu 0.02 
0 
+J 
iU 
!:I 
"O 
:..c:i a .OD 
0 
tf.l 0 50 100 L60 
'--' 
Dose ( MGy) 
Figure 3.17. Effect of Dose on the Formation of Solid 
Ma t e rial in the Electric Discharge of CH.:i-~-I:-kO . 
calculated from the slope of the curve given in Figure 
Figure 3 . 18 shows the chemical yields of this 
water - insoluble material in terms of carbon, hydrogen, 
nitrogen, oxygen, and chloride as calculated from 
eleme ntal analysis obtained at various doses. The 
chemical yields for this material were calculated from 
extrapolation to infinitesimal conversion and were 
133 
,oo 
0 
1 ft 10-
V 
G V ------,,.-
- 2 D 
10 
,a D 
- 3 - ... 10 ... J 
0 50 100 150 
Dose ( MGy) 
Figure 3.18. Dose Dependance of the Chemical Yield of 
Soljd Mater ia l in terms Carbon ( 0 ), Hydrogen ( ~ ) , 
Ni t rogen ( D ) , Oxygen ( v ) and Chloride ( i, ) . 
d e termined t o be: G 0 (H, C) =0.25; G 0 (N) =0 . 042; 
G 0 (0) =0 . 054 ; and G 0 (Cl) =0 . 0019 . 
Th e fun c tional groupings of the oligome ric mate -
rial were not investigated. The empirical formula was 
c a l c ulated to be : C12eH12eCkaN:zCl . The main atomic 
constituents were carbon and hydrogen at one to one 
ratio . The primary interest in the quantitative 
analysis of this material was exclusively to obtain a 
balanc e for the prcxlucts as completely a s pos sible. 
134 
Material balance . Table 3.1 summarizes the initial 
chemical yi e lds {G O ) for the analyzed products in the 
electrjc discharge expe riments. Ac :et.ylene and ethylene 
were the most abundant products, followed by the oligo-
me ric materia l , acetaldehyde, hydrogen cyanide, butyr-
aldehyde, and finally propionaldehyde. In order to 
maini,a in a mat,erial b a lance, tbe chemica l yield(s) of 
decomposition of solute(s) must equal to the chemical 
yi e ld s of identified and unknown products. For the 
Tabl e 3.1. Initial chemical yields (GD) in the elec-
trolys is of gaseous CH..,. - N2 - fbO. 
Compound GD 
- CH..,. 6.54 
- N2 1. 26 
C2fk 2. 14 
C2Ho 0.57 
HCN 0.26 
CfhCHO 0.13 
CH3 CfkCHO 0.011 
CH3 ( Cfb ) z CHO 0.016 
Solid Material: 
C 0 . 25 
H 0.25 
0 0 . 054 
N 0.0042 
Cl 0.0019 
135 
case of carbon, the following expression is derived: 
G O O O O ( - CH. . ) - 2G ( C2 Eh ) -t 2G ( C2 H.,,, ) + G ( HC N ) + 
2G O ( CH:,s CHO ) + 3G O ( CH"' CI-b CHO ) + 
4G 0 (Cl-b(Cfb) 2 CHO) + G 0 (Solid mater1aJ) + 
G 0 (Unknown products); 
where, 6. 54 :_::, 6. 29 + G O ( Unknown products); G O ( Unknown 
carbon containing products) ::c? 0. 25. The identified 
products represent approximately 96% of the initial 
carbon-contain ing products in the electrolysis of the 
CH.,. - N~ - Ik O mixture. 
For case of nitrogen, HCN and the oligomeric 
material were the only nitrogen-products identified, 
and the following expression is obtained: 
2G O ( - N:z) = G O (HCN) -t G O ( Solid material) + 
G 0 (Unknown products); 
where, 2 . 52 = 0.26 + G 0 (Unknown products); therefore, 
G 0 (Unknown products)= 2.26 . 
These calculations indicate that about 96% of the 
total methane and 10% of the total nitrogen were con-
verted into the identified products in the early stages 
of electrolysis of the gas mixture. A number of other 
136 
producLs are also formed in the experiments such as 
amino acids (Kobnyashi and Ponnamperuma, 1985); 
however , they are formed through secondary reacLions 
invo]ving the primary products, e.g., ~Eb, C2 fb , 
CH ~CHO, HCN, eLe. 
Th e resu]Ls presented in -Lhis sec-Lion ennl>le us to 
infer possible reaction schemes that may operate in the 
c lec-Lrolysi s of a CEL. - N2-fbO mixture. The next section 
deRJs with this topic . 
3.3.2. Reaction mechanism 
A pos s i bl f! reaction mechard sm was developed to 
accour1L for the observed chemical changes described in 
the previous section. The reaction mechanism was 
tested by computer simulation using ACUCHEM (see Chap-
ter 2, section 2.8) to evaluate its potential to ex-
p] ain the early stages of electrolysis of a CI:-L. - N::e - EkO 
mixture. 
During the irradiation of the gas mixture, the 
electrons from the electric discharge interact with gas 
molecules producing excited gas molecules (Reactions 
3.1 to 3.3) (Bossard et al., 1983). The probabi]ities 
137 
of interaction depend on the concentration 0 f each gas 
in the mixture, and are 37.5% for either methane and 
nitrogen, and 25% for water vapor (deno~ed by H~O) _ 
e 
CB,. CH,. ... 
( 3 . l ) 
e 
NZ ~ .. 
(3 . 2) 
e 
EbO - ---t Ek 0--
( 3. 3) 
Th e exc jte d molecules produced in reac tions 3 _ 1 to 
3. 3 may undergo dissociatjon producine fref-! r1:1djc:a]s_ 
Exci Le d water molecules (EkO*) dissoc iate producing 
hydrogen atoms (H? } and hydroxyl radicals (HO? ) (Reac -
tion 3 . 4) (Spinks and Woods, 1976; Maurey et al., 
1901) . Excited methane could dissociate producin11 
Cfb?, : Cfb and :CI1? radicals, reaction 3.5 (Slager and 
Blac k, 1982; Bossard et al . , 1983). Computer fittinrr 
of the experimental data suggests that channel 3.5a is 
the major dissociation reaction accounting for 87.5%; 
whereas channel 3.5b and c were less important. 
H2 0- H? + HO? (3 . 4) 
138 
CH ~. - + H. (87 . 5%) (3 . 5 a ) 
I 
cu .. - I : : Cfb + 2H? (11. ox) (3 . 5b) : CH? + 3H? (l.5%) {3 . 5 c ) 
Nitrogen mo l ecules we r e found t o be stable to 
e l cc: t .rolysis in a CII,. - N::z - f-h- 0 mixture , and only a small 
p e r centane of the nitrogen decompos ed in the early 
s t .a ges o f e lectrolysi s , reac tion 3.6a . Computer simu -
lation suggests that channels 3.6a and b represent 
0. 2 5% a nd 99.75%, respectively. 
?N: + ?N: (0.25%) (3.6a) 
N::z + hv {99.75%) {3.6h) 
Compute r fitting of the reaction mechanism (reac -
tions 3 . 1 to 3.30) with the experimental results of 
decomposition of CH,. and formation of C2H:z, C:zHo, HCN, 
and C::z H.q, indica-Le that the rate of production of elec-
trons {e ) in the electric discharge was 7.95X10- 3 elec -
tro n s MGy- 1 and its yield was calculated to be G 0 , (e) = 
121. 5. Table 3.2 summarizes the predicted radical and 
mo lecular yields of primary species obtained by 
139 
Table 3.2. Predicted radical (R) and molecular (M) 
yield s (GR,,M} in the electrolysis of CH.. - N:z, - fko. 
Spec ies 
Gf"II./M 
Cfh? 
:Clk 2 6.42 
: CH ? 3.32 
H? 0.45 7
H 0O .? 76 
. N : 36.34 
0.
- 2C 7H   ... 
- N~ 30.20 0.14
-l  kO 36.34 
simulation of the electrolysis of CH ... -N2-EkO. Cfh?, 
H?, and HO? are the major radicals, and :Cfk, :CH? and 
? N : are produced in low yield. Supporting evidence for 
the formation of CEbs?, :CEk, :CH?, Ek and H? is 
provided by their spectroscopic identification in the 
electric discharge of gaseous methane (Peters and Wag-
ner, 1931; Harkins and Jackson, 1933; Willey, 1934). 
Water vapor was constantly produced during the ex-
periments by maintaining the aqueous phase at 60?C. 
The vapor pressure of water was 149.38 Torr at 60?C 
(Weast et al., 1985). The equilibrium reaction of 
140 
liquid water {denoted by fkO (1)) going into water 
vapor is given by reaction 3.7; the equilibri?um 
con-
stant was calculated to be l.3Xl0-- 4 , taking into ac-
count the concentration of water vapor and liquid 
wate r. 
Ek O ( 1) fbO 
(3 . 7) 
An additional source of water vapor was its refor-
mation from the reactions of hydroxyl radicals with 
hydrogen atoms {reactions 3.8 and 3.9). The rate con-
stant for reaction 3.8 is 2.2X1016 1 2 dm6 mole-2 ? s-1 
(Tsang and Hampson, 1986), while that for reaction 3.9 
is 1. 5Xl019 1 2 6 ? dnf' mole- 2 s - 1 (Wilson, 1972). 
H? + HO? + tb fbO + tb (3.8) 
H? + HO? + fbO fbO + fbO (3.9) 
In addition to the formation of water molecules, 
hydroxyl radicals could dimerize producing hydrogen 
peroxide (reaction 3.10); the rate constant for such a 
reaction is 2.4X1011 (T/300)-0 7 ? dnf' mole-2 s - 1 
(Baulch, et al., 1982). 
141 
HO? + HO? (3. 10) 
Molecular hydrogen was not examined in thi s work, 
but supporti ng evidence for its formation was provided 
by the studies of Wi ene r and Burton (1953), Toupance et 
al. (1 975), and Bossard et al. (1983) on the electro -
lysis of methane and/or me thane - nitrogen mixtures . 
Formation of molecular hydrogen is predicted by di -
me ri zat ion of hydrogen atoms, reactions 3.11 to 3.12; 
the rate constants are 5.4X1012 1 1 3 dm6 mo1~- 2 ? s- 1 
( Cohen and Westberg, 1983; Tsang and Hampson, 1986), 
and 1 . 0X10 1 3 1 1 dm6 mole- 2 s - 1 (Cohen and Westberg, 
1983), respectively . 
H? + II? + N:z 1-k + N:z (3.11) 
H? + H? + 1-kO 1-k + E-bO (3.12) 
Methane molecules were re- formed in the electric 
discharge according to reaction 3.13; the rate constant 
for such a reaction is l.2X1012 1?? 4 dm3 mole- 1 s - 1 
(Tsang and Hampson, 1986). 
+ H? (3.13) 
Methyl radicals may also dimerize leading to the 
formation of ethane, reaction 3.14; the rate constant 
142 
f o r this reaction is 1.0X101 2 1?? 04 dm3 mol e- 1 s - 1 
(Tsang and Hamps on, 1986). A minor los s of me thyl 
radi ca l s may b e attr i buted to its reaction with me thyl -
ene radicals which could lead to the formation of 
ethylene, reaction 3 . 15; the rate constant of such a 
r eac tion i s 4 . 2X10 1 0 dm3 mol e- 1 s - 1 (Tsang and Hampson , 
198 6) . 
Cih ? + c~- (3.14) 
CH-.., ? + :CE-k (3.15) 
Acetyl e ne may be formed by collision of two CEb 
radicals, reaction 3.16 (Weiner and Burton, 1953); this 
r eaction bas a rate constant of 3. 2X1010 dm3 mole- 1 s - 1 
(Tsang and Hampson, 1986). Acetylene may also be 
forme d by dimerization of two CH radicals, r e action 
3. 17 (Braun et al., 1967). Tbe rate constant for suc h 
a r eaction i s 1 . 2X1011 dm3 mole- 1 s - 1 (Braun et al., 
1967) . An additional source for CH radicals could b e 
a t tribute d to the reaction of hydrogen atoms with 
methylene radicals, reaction 3.18; the rate constant 
for this reaction is 1 . 6X1011 drrr mole- 1 s - 1 (Tsang and 
Hampson, 1986). 
143 
:Clb + :CI:-k Ckib + I:-b (3.16) 
:CH? -f : CH? C:z I:-b (3.17) 
:CH::2 + H? : CH? + I:-k (3.18) 
Formation of hydrogen cyanide may be explained by 
t,b p, reaction of CH"" and Cfk radicals with atomic 
nitrogen, reactions 3.19 and 3 . 20, respectively (Bos -
sard et al., 1983) . Tbe rate const,ants for these reac-
tions have been estimated by Yung et al. (1984) to be 
3 . 0X1010 exp( - 250/T) dm"" mole- 1 s - 1 (13). 
CH-:!- ? + . N: HCN + Ek (3.19) 
:Cfk + . N : HCN + H? (3 . 20) 
Nitrogen atoms may also dimerize to form molecular 
r1itrogen, reaction 3.21; the rate constant for such a 
reaction has not yet been determined; however, it can 
bP. estimated by analogy to the dimerization of atomic 
oxyeen (reaction 3.22), for which a rate constant has 
been de1.,ermined to be: 1.9X107 exp(900/T) dm6 mole- 2 
s - 1 {Tsang and Hampson, 1986). 
2 ? N: N::z N::z {3.21) 
2 ? O? + N::z ~ (3 . 22) 
144 
He ac ti o n s 3 . 1 to 3.22 were used to mode l the elec-
tro lys i s of a Cfl,. N2 - ~ 0 mixture. Fi~ure 3 . 19 s hows 
t h e comr1u-Ce<l t rend s of decomposition of CH,. and N2 , and 
t h e f o rmat j on of fb, C:2 Ih , C2 H6 , C2 H,. and IICN in the 
elccL r o ]ys i s o f t h e CH.,, - N2-IL O mixture . Th e b e havior 
p r e d i c t ed h y compute r simu l ation i s essential l y similar 
to that f o und e xperi menta l ly ( see F igu re 3 . 19) . At 
doses abo v e 3 0 MGy the computed tendenc i es d e v i a te from 
t,h e experime nt,a] tre nds mainly b ecause t h e a ccumulation 
produc t s a nd d ecomposition of the i nit ial products 
compli c a-Les the reaction mech anism, and comp uter 
sim11lations cannot b e d on e with existin g expe r i mental 
d a ta for doses l a rge r than 30 MGy. 
Co mputer simulation enable u s to predict the 
c h e mi c al y ield o f format ion of HCN under a v a riety of 
condi t ions that were n ot e xpe r i mentally examined. 
Figu re 3.20a s h ows the compute r trend {solid l i n e ) fo r 
G 0 (HCN) as a fun c tion of the molar ratio for nitrogen, 
nN2 / { nCR,. + nN:z). G 0 (HCN) increases linearly with 
i n crea s ing nitrogen conte nt in the mixt ure, up to a 
maximum , and then sharply decreases down to zero when 
145 
0.02 LO 
r<) 0.02 Q H2 X 
I 
E r-') 
"'O N2 I 
0.01 0.01 l.. E 
~ A "O 
0 V 
E w _. -~Cll4 V 0 
O.G(i .- ~ 0 0 D C 0.00 E 
0 50 ' 100 150 0 50 100 150 
0 ____ ....__ 
0 LC") 
1 
0.02 (, d 0
X . 02 X 
t'i HCN ? I') 
I I 
E 0.01 C2ll4- ? ? 0.01 E 1J -0 
........ .... ....... .. 
Q) 
I} 
0 0 
E 0.000 50 100 150 0 50 100 150 0.00 
E 
Dose ( MGy) Dose ( MGy) 
F igure 3 . 19. Computer Simulations of the Electrolysis 
of a CH,. - ~ - (kO Mixt,ure. Solid lines were obt,ained by 
ACUCHEn using reactions 3.1 to 3.22, and were plotted 
with experimental values (symbols) for comparison. 
Dott,ed lines are simulations of un-analyzed products. 
no methane is present. Experimental support for such a 
trend was obtained by Raulin et al. (1982) who inves-
tigated the effect of initial nitrogen on the electro-
synthesis of HCN. Their data (symbols) has been plot-
ted in Figure 3.20a for comparison, and as can be seen, 
the r e i s a very good correlation between computed 
trends and expe rimental results. 
146 
12 0.2'4 
'z' a ~ ,-.. b .i '-' 0 .40 z Qi 
.I.. ..., ?"? (.) 
100 
I ">. 
.. z .._, z 6 u g 0.12 u 
(.') 0.20 8 J: (_') 50 J: 
0 ~ 
0 "0'  
0 .00 D 0 .0 0 
().0 0 0 .2~ o.-,o 0.7!) 1.00 0.00 0.25 0.50 0.75 1.oi 
nNz / ( nCH~ + nN2 ) nH2 / ( nCH4 + nN2 + nH2 ) 
Preigure (TDrT) 
200 -4-00 600 BOD 
C d 
,-.. .z.- ,, 0.30 z 
u 0 
~J 0.15 :r 
., '-..I 
0 
0.00 
0.00 0.25 0.50 0.75 1.00 50 7';) 100 
Temperoture ("C) 
Figure 3.20. Computer Simulations of the Effect of 
G 0 (HCN) on the molar ratio of Nitrogen (a), Hydrogen 
(b), Wai.er vapor (c), and also as a function of Pres-
sure and Temperature (d) during the Electrolysis of a 
CII" - N:2-IkO mixture. Lines were obtained by ACUCHE/'1 
u s ing reactions 3.1 to 3.22 (a, c, d) or to 3.23 (b) 
and were plotted with published values for comparison: 
( 0) Raulin et al. (1982); and (?)Stribling and 
Miller (1987). The total concentration of gas phase 
molecules was 2.879X10- 2 mole dm- 3 except in (d) where 
it was changed accordingly to the pressure change. The 
concentration of water vapor was kept constant in all 
cases (7.19Xl0-3 mole dm- 3 ) except in {c) where it was 
varied from Oto 2.879Xl0- 2 mole dm- 3 . CI:k and N:z were 
present in one- to-one ratio, except in (a) where it 
varied from Oto 1. 
147 
Raulin et al. (1982) and Stribling and Miller 
(1987) have investigated the effect of added hydrogen 
on the synthes is of HCN. Computer simulations can al so 
pre d ict the trend of G 0 HCN a s a function of the molar 
ratio for f:b, but i t is n eces s a ry to include rea ction 
3.23 t o a ccoun t for the electric discharge dissociation 
of mo l e cular hydrogen into atomic hydroge n. Figure 
3.20b shows the computer trend (solid line) and expe r i -
mental behavior (symbols) as a function of the molar 
rati o for hydrog en. G 0 (HCN) is maximum in the absence 
of hydrogen ; the yield decreases line arly with increas -
ing hydroge n content, d own to zero in the absence of 
eithe r CH4 and N:z. A similar behavior as for hydrogen , 
is al so predi c ted as a fun c tion of water vapor in the 
mixt ure {see Figure 3 . 20c ). 
e 
Eb H? + H? (3.23) 
The total pressure and/or the temperature of the 
gas phase does not have any effect on the yield of HCN 
as predicted by computer simulation (see Figure 3.20d). 
Therefore , G 0 (HCN) depends only on the composition of 
the gas mixture . 
148 
The r esults presented in this sec tion ma y be u sed 
to p redict the p ossible produc tion of HCN by el ectri c 
discharges i n t h e pr i mi tive atmosphere ; this is con-
sid ered in the n e xt s ection. 
3.3 . 3 . HCN synthesis in primitive atmospheres 
At mosphe ric elec tricity is a poorly understood 
s ubje ct , and no estimates of the energy available from 
this s ource on the primitive Earth have been made {Fox 
a nd Dose , 1977) . Cloud electrification is a common 
phenomenon in the atmosphere {Weast, et al., 1986) . 
The p roces s es by wh i ch the charges in a cloud are 
fo rmed and separated are still controversial (Bar- Nun, 
1981 ) . The most common forms of neutralizat ion of the 
c h a rge s are by intracloud and cloud- to- ground dischar-
ges ; the former is more abundant by a factor of about 5 
than the latter {Bar- Nun, 1981) . 
It has been calculated that the flux of lightning 
ene r gy i n the tropics is about l . 5X1019 J cm- 2 y- 1 
{Bar- Nun, 1981) . In mid- latitudes, the number of 
lightning strokes is much smaller and in high lat i tudes 
t hunde rstorms are rare {Bar- Nun, 1981). The globally 
,-------
149 
averaged energy input by electrical discharges 
projected per square- centimeter surface area of the 
Earth is about 16.74 J cm- 2 y - 1 (Fox and Dose , 1977). 
This value includes 3.77 J cm- 2 y- 1 due to lightning 
and about 12 . 55 J cm- 2 y- 1 due to corona discharges 
from pointed objects (Miller and Orgel, 1974). ? The 
quantity of electric discharges that occurred on the 
primitive Earth is unknown (Fox and Dose, 1977); 
however, it is generally accepted that electric dis -
charges were as abundant in the primitive atmosphere as 
are today; and therefore, an energy flux of 16.74 J 
cm- 2 y - 1 has been extensively used to estimate the 
electrosynthesis of organic compounds in the primitive 
Earth (Miller and Orgel, 1974; Stribling and Miller, 
1987) . A dose rate of 1.04X102? eV cm- 3 y- 1 or 13.9 
MGy y- 1 is derived for electric discharges. 
The composition of the primitive atmosphere is not 
known precisely (Fox and Dose, 1977); although it is 
usually accepted that an atmosphere composed mainly of 
methane, nitrogen and water could be reasonable for the 
initial stages of development of the Earth (Ferris and 
Chen, 1975; Bossard et al., 1982); however, there is 
150 
no estimate on the relative proportions of CH N 
4 , ~ and 
EkO in the primitive atmosphere. 
In this study we carried out an extensive 
1?n ves-
tigation to determine the chemical yield of formation 
of HCN from the electrolysis of a gas mixture composed 
of C~ (36.7%), N:z (36.7%), and EkO {26.6%); and a 
G0 {HCN) =0.26 was experimentally determined. Computer 
simulations predict that 0 G (HCN) could vary from a 
factor of 2 to 4 depending on the composition of water 
vapor or nitrogen in the gas mixture, respectively_ If 
we consider these effects, G0 (HCN) could have varied 
from 0.1 to 0.4 depending on the initial nitrogen and 
water vapor content of the primitive atmosphere. If we 
take into account the dose rate of electric discharges 
in the atmosphere, and consider that G 0 (HCN) could 
have varied from 0.1 to 0.4 depending on the atmos -
pheric conditions, an estimate for the rate of electro-
synthesis of HCN in the primitive atmosphere would vary 
Table 3.3 summarizes the chemical yields of HCN 
synthesis and estimated HCN production in the primitive 
atmosphere triggered by various energy sources. Shock 
waves are the most efficient energy source for the 
synthesis of HCN, followed by ionizing radiations and 
151 
Table 3. 3. Est imated productions of HCN in the pr1m1.-
ti v e a-Lmosphere by diffe r ent energy sources. 
En e rgy source G O ( HCN) HCN production 
(mole dm- 3 y - 1 ) 
UV light negligible 1 n eg ligibl e 
Ionizing radiation: 0.01 - 0 . 9 2 
Upper atmosphere 10- 0 - 10- 4 
Lower atmosphere 10- '5-10- 1 
Electric Disc harges 0.1 - 0 . 43 
Shock waves 3. 2 4 
Tota l 
1 . Raulin et al., 1982; 2. Zhdamirov et al., 1970; 3. 
This study; 4. Bar- Nun and Shaviv, 1975. 
electric discharges. Ultraviolet light has been found 
to contribute negligibly to the HCN synthesis (Raulin 
et al. , 1982). The estimated total production of HCN 
in the primitive atmosphere would b e about 1010 - 1019 
Fegly et al., (1986) have derived 
a HCN rainout rate of (3 - 14)X1011 mole y- 1 ; this indi -
cates that HCN synthesized in the primitive atmosphere 
would be efficiently transported into the oceans by 
precipitation processes. 
152 
The physical conditions of the primitive Earth are 
not, known but it is believed that they did not change 
significantly during the history of the Earth (Ferris 
and Hagan, 1984). If we assume that the volumes of the 
at.mosphere and hydrosphere have not changed, and if all 
UCN synt.hesized in th e atmosphe re would b e dissolved in 
the hydrosphe re without any loss due to HCN hydrolysis 
and / or oligomerization, the concentration of HCN in tbe 
hydrosphere would vary from 10- 3 to 10-- 2 mole dm- 3 y- 1 ? 
These figures represent only the upper limits since HCN 
would b e hyd rolyzed and/or oligomerized in hydrosphere; 
howe v e r, as it was discussed in Chapter 1 (section 
1.3) , these values could be increased by concentrating 
mec hanisms suc h as the eutectic freezing of water 
volumes (Sanchez et al., 1967) and by the formation of 
stable cyanocomplexes as ferro and/or ferricyanide (Na-
varro- Gonz.alez , 1983; Navarro- Gonzalez et al ., 1989). 
3.4. Conclusions 
Thi s study describes and characterizes three new 
me U1od s 1,o <l e i.,e rmine the dose rate supplied by high 
frequency, high voltage electric discharges. The dose 
153 
rate was calculated to be 2.73 0 . 042 MGy hr- 1 , and was 
found to b e ind e pendent of the chemical composition of 
the system. Knowledge of the d ose r ate of electric 
dischar ge experiments was essential to study the elec-
tro l ysis of a simulated prim i tive atmosphere, and to 
ac:r.urate 1y dete rmin e the chemical yield s of solutes and 
produr.ts. 
The electrolysis of a gas mixture compos ed of 
0. 01 OB mole drrr""' of mf'!thane, 0. 0108 mol e dm- 3 of 
nitrogen, and 0.00782 mole dm- 3 of water vapor 1n equi -
librium with a liquid phas e of 0.05 mole dm- 3 aqueous 
ammonium chloride buffer at pH 8.7, was investigated at 
60?C and 600 Torr in the dose range from 0.38 to 
15 2 .30 MGy. Th e initial chemical yields of decomposi -
tion of methane and nitrogen were determined to b e 6 .54 
and 1 . 26, respectively. About 96% of the initial 
methane and 10% of the initial nitrogen were converted 
into: C2 ~ (G 0 =2 . 14), C::z lb (G 0 =0.57); HCN (G 0 =0.26); 
CH .:e: CHO (G 0 = 0.13); CfhCfbCHO (G 0 =0.011); CH3 (Cfb)::zCHO 
(G 0 =0.016); and unidentified water-insoluble oligomeric 
materia l (G 0 =0.25 for carbon). 
A free radical chemical mechanism was developed to 
account for the chemical changes produced by electric 
154 
discharges . Computer simulations of this mechanism 
can effectively model the early stages of electrolysis 
of the gas mixture; the following radical yields are 
predicted: G0 (CI-h)=26.42; G0 (Cfk)=3.32; G0 (CH) =0.45; 
G 0 (H) =70.76; G0 (H0) =36.34; G0 (N)=0.27. 
Computer simulations of the electrosynthesis of 
IlCN under a variety of conditions (e.g., chemical com-
position, pressure, temperature) were carried out in 
ord e r to establish the effect on G 0 for HCN. These 
studie s indicate that the chemical yield of HCN does 
not depend on the gas pressure and/or temperature, but 
does depend on the chemical composition of gas mixture, 
varying by a factor of 2 or 4 depending on the relative 
abundance of nitrogen and water or hydrogen in the gas 
mix-Lure. 
The possible rate of electrosynthesis of HCN in 
the primitive atmosphere was estimated to vary from 
10- 4 to 10- 3 mole cm- 3 y- 1 depending on the atmos -
pheric conditions, and for which G 0 (HCN) was consi -
dered to change from 0.1 to 0.4. In addition, the 
possible contributions of other energy sources to trig-
ger the synthesis of HCN in the primitive atmosphere 
155 
were considered, and a possible total rate of HCN syn-
thesis was estimated to be: 10-2 - l0- 1 mole cm- 3 y - 1 ? 
From such a valu e , it can be estimated that the 
possible upper limit for the concentration of HCN in 
the hydrosphere would have varied from 10- 3 to 10-2 
mole dm- 3 y - 1 . 
The concentration of HCN in the primitive hydro -
sphere may have been increased by mechanisms such as 
the eu~ectic freezing of water volumes (Sanchez et al., 
1967) and by the formation of stable cyanocomplexes as 
hexacyanoferrate(II) and/or {III) (Navarro- Gonzalez, 
1983; Navarro- Gonzalez et al., 1989), as already 
discussed in section 1.3 (Chapter 1). The presence of 
cyanocomplexes of metal ions such as hexacyano-
ferrate(II) and/or {III) in the primitive hydrosphere 
could have been important to promote abiotic organic 
syntheses (Beck, 1978; Kobayashi and Ponnamperuma, 
1985). Chapter 4 describes the potential of such 
species in promoting the free- radical oligomerization 
of HCN in aqueous solution. 
L_________ - -
156 
CHAPTER 4 
THE EFFECT OF CYANOCOMPLEXES ON THE FREE-RADICAL 
OLIGOMERIZATION OF HYDROGEN CYANIDE 
4.1. Introduction 
Transition metal ions are generally believed to 
have played a role in the process of chemical evolu-
tion because of their wide distribution on the Earth 
crust and also because they are ubiquitous among living 
systems (Kobayashi and Ponnamperuma, 1985a). Beck 
(1978) has suggested that the transition metal ion 
content of the primordial and contemporary sea water 
could differ by several orders of magnitude based on 
the dissolving capacity of cyanide: A dilute cyanide 
solution (10- 2 mole dm- 3 ) readily dissolves transition 
metal ions from igneous rocks (Beck, 1978). The author 
has further suggested that the rate of hydrolysis of 
HCN in the primitive hydrosphere might have also been 
157 
small on account of its coordination with metal ions 
leading to the formation of cyanocomplexes of transi-
tion elements (Beck, 1978). 
Cyanocomplexes of iron are characterized by their 
high solubilities (Weast et al., 1985) and high stabi -
lity constants (Smith and Martell, 1976). They have 
been postulated as probable candidates for playing 
crucial roles in promoting the synthesis of prebiotic 
compounds in the primitive Earth (Beck, 1978, and 
references therein); however, only a limited number of 
studies has been devoted to examine the effects of 
metal ions in catalyzing reactions of abiotic 
significance (Kobayashi and Ponnamperuma, 1985a,b) . 
Furthermore, hexacyanoferrate(II) has been found to 
possess enzyme-like activity, and has been suggested as 
an intermediate in the evolution of iron- containing en-
zymes (Kammaludin, et al., 1986). 
The purpose of this study was to provide 
experimental evidence of the possible role of cyano-
complexes of iron on the free-radical oligomerization 
of HCN. Hexacyanoferrate(II) or (III) readily reduces 
or oxidizes a variety of free radicals (Ross and Neta, 
1982; Buxton et al., 1988). Therefore it was 
158 
considered important to study the effect of hexacyano-
ferrate(II) and (III) on the fate of the free- radical 
oligomerization of HCN. 
An extensive investigation wa s carried out to 
study the free radical reactions initiated by the 
radiolysis of liquid water (H., HO. , e..q - ) with hexa-
cyanoferrate(II) and with mixtures of HCN and hexa-
cyanoferrate(II) or (III). The results and discussions 
of this study are given below. 
4.2 The ~-irradiation of aqueous hexacyanoferrate(II) 
The radiation chemistry of hexacyanoferrate(II) 
and (III) is fairly well understood in pulse radiolysis 
experiments carried out at high dose rates in the 10- 6 -
10-3 s time scale {Rabani and Matheson, 1966; Rabani 
and Meyerstein, 1968; Zehavi and Rabani, 1972, 1974); 
howeve r, the data presently available are not suffi-
cient to explain the radiolytic behavior of bexacyano-
ferrate(II) at low dose rate experiments (as those 
usually done with 6 ?Co-~-sources). in particular. in 
anoxic solutions (Masri and Haissinsky, 1963; 
159 
Haissinsky et al., 1966). We were prompted to inves-
tigate this system in order to determine if the cyano 
group coordinated to the metal ion could contribute to 
the formation of organic compounds. 
Aqueous, oxygen- free, 0.02 mole dm- 3 K4Fe(CN)6 
aqueous solutions (pH 6.6) were irradiated with 6 ?Co-
~ - rays in a wide dose range from 0.1 to 690 kGy. 
Figure 4.1 shows the decomposition of hexacyano-
ferrate(II) as a function of dose; its concentration 
decreased linearly with increasing dose during the 
early stages of ~-irradiation (Figure 4.1a), but as the 
dose increased above 200 kGy, it approached a steady 
value of about 0.0145 mole dm- 3 (Figure 4.1b). The 
initial radiation chemical yield (G?) of decomposition 
of hexacyanoferrate(II) was calculated from the slope 
of the curve in Figure 4.1a, and was determined to be 
1.15. 
The dotted line shown in Figure 4.1 was obtained 
by computer simulation of the reaction mechanism using 
ACUCHEH (see Chapter 2, section 2.8). The reactions 
included in the simulations consist of those produced 
during the irradiation of liquid water: Reactions 1 to 
54 given in Tables 2.3 to 2.7 in Chapter 2, section 
160 
2 . 1 
N a 
.0,.. ... 
2 .0E I> . OCQoo. 
-X Cb .. ..... .. ..... '?? .... ' 0 ?????'. t0 1 .9 
I C'l 
E 
"D 
1 .8 
(1) 0.0 2 .0 4.0 6 .0 8.0 
0 
E 
,.__,.. 2 . 
b 
,---, 
I 
"<t" 
....C....D...  
z 
-u- 1.0 cu 
Li... 
'--' 
0.5 
0 200 400 600 800 
Dose ( kGy) 
Figure 4.1. Decomposition of bexacyanoferrate(II) at 
low (a) and high dose (b) of ~- irradiation of a 0.02 
mole dm- ~ K4Fe{CN)o aqueous solution. Dotted line was 
obtained by computer simulation of the reaction 
mechanism (see text for details). 
2 . 8. The overall process of water radiolysis may be 
summarized by reaction 4.1: 
161 
IkO ---+ HO? + H? + e.q + W- + Eb + EbCh { 4. 1) 
In addition to such reactions, computer modeling of the 
irradiation of aqueous solutions of hexacyanoferrate 
(II) included reactions 4 . 2 to 4.22 that are described 
below. 
Hexacyanoferrate(II) reacts with hydroxyl radi -
cals according to reaction 4.2 leading to the formation 
of hexacyanoferrate(III) and hydroxide ion: 
HO? {4.2) 
The rate constant of this reaction has been determined 
in pulse radiolysis experiments by Zehavi and Rabani 
{1972) to be l.25X1010 dm~ mole- 1 s - 1 ? As the concen-
tration of hydroxide ion, G 0 =0.59, starts to increase 
with dos e (Figure 4.2), the pH of the irradiated solu-
tions increases from 6 . 6 to about 11 {Figure 4.3) . 
Under these conditions, hydroxyl radicals dissociates, 
reaction 4.3 {Draganic and Draganic, 1971), and the 
radical-anion {?O-) reacts with hexacyanoferrate(II) 
{reaction 4.4) with a smaller rate constant, 1.5Xl09 
dm-3 mole- 1 s - 1 (Ross and Ross, 1977). 
162 
... 
0 
3.0 
n-X  
I 
E 2.0 
"O 
II 
0 
E , .0 
'-' 
,-, 
I 
:i 0 . 
.0__ , 0.0 2.0 4.0 6.0 8.0 
Doae ( kGy) 
Figure 4 . 2. Dose dependance of the concentration of 
hydroxide ion. 
12.0 
... ... . ....... ........ . ?????? 0 0 0 
~ 0 
pH 9.0 0 
() 
6.0 
0 4 8 12 
Do!IB ( kGy) 
Figure 4.3. Variation of pH with irradiation dose of 
an aqueous solution of K...Fe(CN)6. Dotted line was ob-
tained by computer simulation (see text for details). 
163 
HO? . o- pK =ll . 7 {4 .3 ) 
fbO 
?O- + Fe {CN)6 4 -
He xacyanoferrate{III) was identified in the ir-
radiated solutions by spectroscopy . Figure 4.4 shows 
the spectra of an irradiated solution {dashed line ) and 
o f s t andard solutions hexacyanoferrate{II) {dotte d 
line) and hexacyanoferrate{III) (Solid line ) . The 
'1, 1.2 2 .0 
..;-
)( 
)( 
....... 0.9 1.5 
~ 
I u 
5 C 
CJ) 0.6 1.0 .8 I,.. 
I ,0,,  
I) 
0 
E 0.3 0.5 ~ 
I') 
E 
"tJ 
........ o.gso ---- , 0.0 450 550 650 750 850 
Wove length (nm) 
Figure 4 . 4. Extinction coefficient of hexacyanoferrate 
(II) (dotted line) and hexacyanoferrate(III) (solid 
line) as a function of wavelength, and absorbance 
(das hed line) of an aqueous solution of 0 . 02 mole dm- 3 
~Fe(CN)6 at 200 kGy . 
164 
formation of hexacyanoferrate(III) was attributed main-
ly to reactions 4.2 and 4.4; a minor source was 
ascribed to the reaction of hydroperoxyl radicals, HOz ? 
{reaction 4.5) with hexacyanoferrate{II), reaction 4.6. 
The rate constant for reaction 4.6 was determined be 
3X10'4 dm3 mole- 1 s- 1 in pulse radiolysis experiments 
carried out by Zehavi and Rabani {1972). 
EkOz + HO? lb O + H<k ? ( 4 . 5 ) 
HO:z ? + Fe(CN)6 4 H<k- + Fe(CN)6 3- - (4 . 6) 
Figure 4.5 shows the formation of hexacyanofer-
rate(III} as a function of dose; its concentration 
linearly increases with dose, G 0 =l.08, and then 
steadily increases at higher doses reaching a steady 
concentration of about 0.004-0.005 mole dm- 3 ? The 
experimental results agree quite well with the trend 
predicted by computer simulation at low doses of 
irradiation (Figure 4.5a); however, at higher doses the 
reaction mechanism complicates due to unknown reactions 
involving the initial products. Computer simulations 
cannot be done at higher doses with existing experimen-
tal data. 
165 
0 .9 
I") a 
0 0 
~ ., ,Q . ... .. ..... 
>< 0 .6 
o? 
..--,.., 
I") 0 
I 0 .3 0 
E o ?? 
-0 
n., ~ 
0 .0 
Cj) 0.0 4.0 8.0 12.0 
0 
E 
--..__; 
9.0 b 
r--, 
I 
I"') 6 .0 
....<...O....  
z 
(.) 
--..__; 
Q) 
L.. 
'---' 
0 . 
0 200 400 600 BOO 
Dose ( kGy) 
Figure 4.5. Dose dependance of the concentration of 
hexacyanoferrate {III) at low (a) and high dose of ~-
irradiation of a 0.02 mole dm- 3 K4Fe{CN)6 aqueous solu-
t ion. Dotted line was obtained by computer simulation 
of the reaction mechanism. 
Hexacyanoferrate{II) may also react with hydrated 
electrons leading to the formation of hexacyanoferrate 
{I), reaction 4.7. The rate constant for this reaction 
has been determined to be ~7X104 dm3 mole- 1 s- 1 in 
pulse radiolysis experiments carried out by Zehavi and 
Rabani {1974). 
166 
(4.7) 
h hexacyanofe
rrate(II) 
ct wit
Hydrogen atom
s rea
the triple car
-
rogen in 
ing to the ad
dition of hyd
lead ction 4.8); th
e 
d (rea
-nitrogen bond
 of the ligan
bon
ined by Zehavi
 and Rabani 
te constant w
as determ
ra  and was found
 
e radiolysis e
xperiments,
(l9 74) in pul
s
d Rabani, 197
4). 
7 drrr mole-
1 s- 1 (Zehavi an
to be 3.9X10
)aFr- (4.8
) 
Fe(CN
H + 
ses, 
 by two consec
utive proces
followed
Reaction 4.8 
is 
 (reaction 4.9
), 
e first one is
 first order
of Which th ediate 
s a reaction o
f the interm
d one i
While the sec
on
avi and 
(reaction 4.10
) (Zeh
ith hexacyano
ferrate(III) 
~
Rabani, 1974)
. 
(4.9) 
N)aH4 + Fe(C
N)a3 -
Fe(C - CN (4.10)
 
CN)a
4
- + H
Fe(CN)~3- + 
Fe(
9 was found to
 
te constant o
f reaction 4.
The ra
03 s-
1 at pH 0-4 (Zeh
avi 
 from 1CJ5 to 1
decrease with
 pH
used in 
 and the lowe
st value was 
),
and Rabani, 1974 of 
eriments, whil
e the rate 
computer simu
lation exp
167 
1 1 
reaction 4.10 was set to 2x10~ dm
3 mole- s - (Zehavi 
and Rabani, 1974). 
Zehavi and Rabani (1974) have suggested that pen-
tacyanoferrate(I) may react with hexacyanoferrate(II) 
and (III), reactions 4 . 11 and 4.12, respectively. The 
authors found that the rate constants of these reac-
tions are pH dependent, and a value of 1X108 dm3 mole-
1 
s - 1 {Zehavi and Rabani, 1974) was used in computer 
modeling . 
N)6 3 - --+ Fe(CN)o3
4
Fe(CN)o 4 + Fe{C - + Fe{CN)6 - {4.11) -
Fe(CN)o4 4- + Fe(CN)6 ---+ Fe(CN)e
3
- + Fe(CN)6e- {4.12) 
Pentacyanoferrate{II) formed in reactions 4.10 to 
4.12, may react with hydrogen peroxide {reaction 4.13) 
or its anion (reaction 4.14) leading to the formation 
of pentacyanoferrate(III). The rate constants for 
these reactions were determined by Davies and Garafalo 
(1976) to be: 107 and 3 dm3 mole-
1 s - 1 , respectively. 
Fe(CN) o 3 - + Ek<k Fe ( CN )02 - + HO- + HO? {4.13) 
168 
HO-+ ?O- (4.14)
 
2
Fe(CN)o - +
pendance for
 
ws the predi
cted dose de
Figure 4.6 s
ho
(III) in the
 
and 
f pentacyano
ferrate(II) 
th e formation 
o
 is predicted
 
ion
tions. Thei
r concentrat
lu
irradiated s
o
kGy), and 
aximum at low
 doses (~2 
to increase 
to a m
ir reactions  of the
th dly decrease
 on account
en rapi /HCN 
.13 and 4.14)
 or with -cN
~ (reactions
 4
With Ek he equili -
4.16), respe
ctively. T
 
(reactions 4
.15 and
been determin
ed to 
r reaction 4
.15 has 
t fo
brium consta
n
ate 
urray, 1975) 
while the r
es and M
be 5X1oa (Ja
m
been found to
 be 
e reverse re
action has 
constant for
 th
-----7 
8.0..-----
--
IO 
0 
X 6.0 . ,. ....... ???- .... '???. , 
,.., 
k 4.o 
u 
II) 
0 
E 
Dose ( kGy) 
n-
on_of p
e
d trends for
 the , f?rmat~ of 
.6. Compute the ~-1rrad1
at1on 
Figure 4  (III) in 
tacyanoferr
ate(II) and ate(II). 
utions of he
xacyanoferr
aqueous sol
169 
6X10- ' s- 2 (Sharpe, 1976). The equilibrium constant 
for reac tion 4.16 is 50 (James and Murray, 1975). 
Fe( CN) o 2 - + - cN (4.15) 
(4.16) 
Th e fate of hexacyanoferrate( I) which is predicted 
to be formed according to reactions 4.7 and 4.12, is 
not known but it is possible that it may react with 
hydrogen peroxide (reaction 4.17) leading to the forma - .. 
tion of hexacyanoferrate(II). Its rate of reaction was 
assumed to be greater than that of hexacyanoferrate 
(II), which is a more stable species, and was set to 
103 dnr mole- 2 s - 2 in computer simulation experiments . 
Fe ( CN )6 e - + f:kO:z Fe(CN)6 4 - + HO- + HO? (4.17) 
Figure 4.7 shows the predicted formation of hexa-
cyanoferrate(I) and hydrogen peroxide as a function of 
dose. The concentration of Fe(CN)6e- is estimated to 
reach a maximum at low dose but rapidly falls off due 
to reactions 4.17 and 4.18; the latter becoming 
dominant at doses above 0.2 kGy. 
170 
co .3.0 
0 
~ 
X Fe(CN)65-
...-.. 2.0 
n 
I 
E 
"O 
1.0 Hz02 .. :?1, ??? ??? ??'" 
IV ??? ?? . 
0 
E 
.___, 
0.0 .? 
0 .0 0.2 0.4 0.6 
Dose ( kGy) 
Figure 4.7. Computed trends for the formation of hexa -
cyanoferrate (I) and hydrogen peroxide in the l:f -
irradiation of aqueous solutions of 0.02 mole dm- 3 
K .. F'e (CN)o. 
(4.18a) 
(4.18b) 
Reaction 4.18 has been studied by Zehavi and 
Raba ni (1974) in pulse radiolysis experiments and a 
rate constant of 2.4X109 dm3 mole- 1 s - 1 was derived; 
channels 4.18a and 4.18b represent 88% and 12%, respec-
tively (Zehavi and Rabani, 1974). 
The hydrogen atom may also react with hexacyano-
ferrate(III} as its concentration starts to build up in 
solution. The rate constant for this reaction is 
171 
5 . 8X109 dm3 mole- 2 s - 2 , and channels 4.19a and 4.19b 
represent 90% and 10%, respectively (Zehavi and Rabani, 
1974). Reaction 4.19 competes with reaction 4.8 and 
becomes dominant at high dose. 
--I~ ---~? Fe(CN)o 4 - + W (4.19a) H? + Fe(CN)o 3 -
-----~? Fe(CN)e 3 - + HCN (4.19b) 
Another source of disappearance of bexacyanofer-
rate(III) was reaction 4 . 20; however, its contribution 
is predicted to be minor as compared to reactions 4.18 
and 4 . 19 . The rate constant for such a reaction is 
relatively small, 2.7X102 dm3 mole- 2 s- 2 (Zehavi and 
Rabani, 1972). 
(4.20) 
As the pH of the solutions increases with dose, 
hydrogen peroxide dissociates according to reaction 
4.21, pK=11.6 (Eaton and Pankratz, 1985), and the anion 
reacts with hexacyanoferrate(III) with a rate constant 
of 99 dm3 moJe- 2 s- 2 , reaction 4.22 (Eaton and 
Pankratz, 1985). 
172 
lkCb a 0:z - + w (4 . 21) 
H0..2 - + F e (CN ) o 3 - (4 . 22 ) 
Comp uter s i mulation expe riments cannot pre d ict 
the actu al tre nds o f produc t s at dos e s above 10 kGy. 
This ma y be du e to secondary reactions that invo lved 
tb e penta cyanoferrates, Fe(CN)"" 3 - and Fe(CN)"" 2 -, with 
hydrogen a t oms , hydrated elec trons and hydroxyl radi -
ca l s. I t ma y also i nvolved complexation reactions with 
stab l e molecules such as molecular hydrogen , which i s 
formed i n the irradiate d solutions (G 0 =0 . 30), but in a 
lower y ield than predicted by computer simulations 
(Figure 4 . 8) . 
Th e irradiated solutions of hexacyanoferrate(II) 
were al so analyzed for the formation of carbon contain -
ing products. Search for carbon dioxide, aldehydes and 
carb oxylic acids gave negative results in the dose 
range studied (up to 690 kGy) with techniques having 
d e tection limits ~10-0 mole dm- 3 . Therefore, the cyano 
group coordinated to the iron complex does not decom-
pose. 
173 
u; 
0 6.0 
>< 
,...._, 
n 
I 4.0 
E 
"O ,,,,.,-P 
Q) 
0 2.0 
..E_,,  
,....., 
N 0. 
I 
L...I 0 .0 0.4 0.8 1.2 
Dose ( kGy) 
F igure 4 . 8. Dose dependance of the concentration of 
mo lec ular hydrogen in the irradiation of aqueous solu-
tions of hexacyanoferrate(II). Dotted line was 
obt a i n e d by computer simulation . 
The results presented. in this section clearly 
d e monstrate that hexacyanoferrate(II) is very reactive 
toward free radical reactions. However, the cyano 
groups coordinated to the metal ion do not participate 
in the formation of organic compounds as does when it 
is not coordinated.. Therefore, it seems likely that 
HCN might have not played a significant role on the 
synthesis of organic compounds in the primitive Earth 
if it was mainly present as a ligand coordinated to 
me tal ions such as iron . 
174 
The effects of hexacyanoferrate(II) in aqueous 
mixtures containing free HCN and hexacyanoferrate(II) 
are discussed in the next section. 
4.3 The ~-irradiation of aqueous hexacyano-
ferrate(II)-HCN mixtures 
Aqueous, oxygen-free solutions (pH :.:-f 6) of 0.1 mole 
dm- 3 HCN and 0.001 mole dm-3 K,.Fe(CN)o were irradiated 
with 0 ?Co-ti' - rays in a wide dose range up to about 100 
kGy. 
Hydrogen cyanide is initially present in solution 
in its non-dissociated form; however during the 
irradiation of the aqueous solution, the pH increases 
from 6 to about 7.5 (Figure 4.9). Under these condi -
tions, hydrogen cyanide is reversibly converted into 
cyanide ion according to reaction 4.23; the rate con-
stants of both forward and reverse reactions are known, 
and are: 5.2X104 dm3 mole- 1 s- 1 , and 3.7X1<P dnr mole- 1 
s - 1 , respectively (Wilson, 1972a). 
175 
8 
pH 
6 
4 +------,------,-----r------1 
0 25 50 75 100 
Dose ( kGy ) 
Figure 4 . 9. Variation of pH as a function of dose 
during the b - irradiation of an aqueous solution of 0.1 
mole dm- 3 HCN and 0.001 mole dm- 3 K...Fe(CN)o. 
- cN + EkO HCN + HO- (4.23) 
The reaction scheme for the radiation-induced 
decomposition of BCN has been examined in detail in 
Chapter 1, section 1.4.2. Hydrogen atoms react with 
hydrogen cyanide (reaction 4.24) with a rate constant 
of 3.3Xl07 dm3 mole- 1 s- 1 , (Ogura, 1968; Draganic et 
al . , 1973), while cyanide ion reacts at a higher rate 
constant (reaction 4.25): 2.6Xl09 dm3 mole- 1 s- 1 (Anbar 
and Neta, 1967). 
176 
HCN + H- RzC=N? {4.24) 
- cN + H- RzC=N- {4.25) 
Hydra ted e l ectrons r e a c t with HCN and - cN a ccord-
i n g to reac tions 4 . 26 and 4.27, respectively. The rate 
con s~ants f o r these reactions are 6 . 6X1<13 dm3 mole- 1 
s - 1 {Dr a ganic et al . , 1973), and 5X105 dm3 mole- 1 s- 1 
{B ie l s k i and Allen, 1977), consecutively . 
fb O 
BCN + e.. "' IkC=N? + HO- (4.26) 
2Ik0 
- cN + e.. "' RzC=N? + 280- (4.27) 
Hydroxyl radical and its anion reacts with HCN and 
- cN a c cording to reactions 4.28 to 4.30. The rate 
constant of reaction 4 . 28 is 6X109 dm3 mole- 1 s - 1 
(Buc hler et al., 1976) while that of reaction 4.29 is 
6.5Xl09 dm3 mole- 1 s - 1 {Kraljic and Trumbore, 1965; 
Behar, 1974; Buchler et al., 1976; Bielski and Allen, 
1977) . The rate constant of reaction of the radical -
anion with cyanide ion {reaction 4.30), is smaller: 
2 . 6X1QB dm3 mole- 1 s - 1 {Behar, 1974; Buchler et al . , 
19 76). 
177 
HCN + HO? HO- CH=N? (4.28) 
- cN + HO? HO- C=N- (4.29) 
- cN + - o - - o - C=N- {4.30) 
The radicals produced by reactions 4.24 to 4.27 
undergo disproportionation reaction (4.31) leading to 
t he re- formation of HCN and formation of H2C=NH. The 
rate of this reaction is l.3XlO9 dm3 mole- 1 s- 1 
(Buchler et al., 1976). 
21:-kC=N? HCN + EkC=NH {4.31) 
Figure 4.10 shows the decomposition of HCN as a 
function of dose. The initial radiation chemical yield 
of decomposition of HCN was determined to be 2.00; this 
value is considerably smaller than that obtained in 
pure aqueous HCN solutions (G 0 =7.6O}. Reactions 4.24 
to 4.31 are not sufficient to account for the decom-
position of HCN in the presence of iC4Fe(CN}b. Analysis 
of data indicates that hexacyanoferrate(II} reacts with 
HO- CH=N? leading to the re-formation of HCN, reaction 
4.32. The rate constant of reaction 4.32 was derived 
by computer simulations and was determined to be 
178 
0 .1 2..------------------
,.,., 
I <D .. 
E .... ,. ,. '. 
-0 0 0 ..... . ' 
0 .08 0 
Cl 
0 
E 
0 .04 
r"""1 
z 
u 
I 
1-..,J 0 .00+-----------------' 
0 25 50 75 100 
Dose ( kGy) 
Figure 4 . 10 . Decomposition of HCN during the ~ -
irradiation of an aqueous 0.1 mole dm- 3 solution of HCN 
and 0 . 001 mole dm- 3 of K....Fe{CN)o . Dotted line was 
obt a i n e d by computer simulation {see text for details). 
5 . 0X1 03 dm3 mole- 1 s - 1 with an estimated error of about 
10% . As the pH of the solution increases with dose, 
HO- CH =N? dissociates with a pK=5, reaction 4.33 (Behar, 
1974 ; Buchler et al . , 1976); the radical - anion formed 
also reacts with bexacyanoferrate{II) according to 
reaction 4 . 34. The reactions 4.32 and 4.34 were undis -
tinguishable in computer simulations. 
HO- CH=N? + Fe{CN)o 4 - --+ Fe(CN)o 3 - + HCN + HO- (4.32) 
HO- CH=N? -o- CH=N? + w (4.33) 
179 
Computer simulation experiments were carried out 
taking into account reactions 1 to 54 which were given 
in Tables 2 . 3 to 2.7 (Chapter 2, section 2.8) as well 
a s r e a c tions 4.2 to 4.54. 
Figure 4.11 shows the formation of hexacyano-
ferrate(III) in the aqueous mixture; its radiation 
chemical yield of formation was determined to be 4.10. 
The origin of Fe(CN)6 3 - was mainly attributed to 
1. 0-.-------------------, 
~ 
0.,.. .... 
,--, X 
I 
r,r') 
co l-....--. "1 
-z I 0.5 
????? .. 
u E 0 ??????????????????????? ?????? ??? 
V 
~ 
._L_._._ , ., 0 0 0 0 
0 0 
f 
..__... 
0 20 40 60 60 
Dose ( kGy) 
Figure 4.11. Formation of hexacyanoferrate(III) 
during the ~-irradiation of an aqueous, oxygen-free 
solution of HCN and hexacyanoferrate(II). Dotted line 
was obtained by computer simulation (see text for 
details). 
180 
r eactions 4 . 32 and 4 . 34, and to a muc h lesser extent 
to reactions 4 . 2, 4 . 4, 4.6, and react ions 4 . 13 and 4 . 14 
followe d by 4 . 15 and 4 . 16 . At doses above 10 kGy, it 
d isappears a cco r d i ng t o r e actions 4.18 and 4.19 . 
Ho we ver, as in the case of the ~Fe(CN)o system (sec -
tion 4 . 2) , compute r simulati ons failed at high doses 
ma i n l y b ecause of the lack of knowledge on the fate of 
the p e n t a c yan oferrates in the mechanism of radiolysis . 
Figure 4.12 shows the experimental and predicted 
dose d e p e ndance o f formation of hydrogen (G 0 =0.45} 
wh ile figu re 4 . 13 presents the predicted formation of 
IO 
0 
6.0 
X 0 
,....,.. --.. 
I +.O ... ?6 
E 
"Cl .o ? 
4) 
0 2 .0 o ? 
E 
.. Cf 
,-, 
N o.~f}-? 
..I.. ..... 0.0 0.4 0.8 1.2 
Dose ( kGy) 
Figure 4.12 . Formation of molecular hydrogen during 
the irradiation of HCN and bexacyanoferrate(II) solu-
tions . Dotted line was obtained. by computer 
simulation. 
181 
v 
0 
4.0-r-----------------, X 
I"') 
I 
E 
'O 
2.0 
Cl) 
0 
E 
.--, 
N 
0 D.0+-------.------,-------1 
N 
:r: 0 .0 2.0 4.0 6.0 .__, 
Do11e ( kGy) 
Figure 4 . 13 . Computer simulation for the formation of 
hydrogen peroxide during the irradiation of HCN and 
K4Fe (CN)6 solutions . 
hyd rogen p e roxide (6? =0 . 59). The mechanism of forma -
t i on of both Ik and EkO:z was considered in detail i n 
Chapter 2, section 2 . 8, and is summarized by reaction 
4 . 1. 
CO:z (Figure 4 . 14} and Nfb {Figure 4.15) are the 
main products formed directly from HCN in the presence 
of h e xacyanoferrate{II}; their initial radiation chemi -
cal yields of formation were determined to be 0 . 60 and 
1.01, respectively . The origin of both compounds may 
be explained as follows . Disproportionation of 
182 
"<t 
0 
.- 1.5,---------------, 
X 
I") 
I 
E 1.0 
'O 
II) 
~ 0.5 
0 
,...., 
~ 0.00;l"------+-----+------+-----+--,1 
o 0.0 0.5 1.0 1.5 2.0 
L......J 
Do:ie ( kGy) 
Figure 4.14. Formation of CO:z during the \::' -irradiation 
of a solution of 0.1 mole dm- 3 HCN and 0.001 mole dm-3 
~Fe(CN)6. Dotted line was obtained by computer 
simulation (see text for details). 
2,0.,.....----------------
X 
,.,, 
I 
E 
'O 
1.0 
Ill 
0 
..E....,  
..---, 
I ""> Q.llfllF-----,--------.------.-----' 
.z.... ... 0.0 5.0 10.0 15.0 
DoGe ( kGy) 
Figure 4.15 . Formation of N~ during the irradiation 
of a solution of 0.1 mole dm- 3 HCN and 0.001 mole dm- 3 
K .... Fe( CN )6. 
183 
HO - CH =N? or - o - CH=N? leads to the formation of cyanic 
acid or cyanate with rate constants of l.1Xl09 dm3 
mole- 1 s - 1 (reaction 4.35) (Behar, 1974; Buchler et 
al., 1976) or 6.5Xl0'3 dm3 mole- 1 s - 1 (reaction 4.36) 
(Behar, 1974), respectively. Cyanic acid or cyanate 
undergo hydrolysis and/or ammonolysis leading to the 
formation of CO:z, NH3 and urea (reactions 4.37 to 
4. 43). The second order rate constants (k) given in 
these reactions have units of dm3 mole- 1 s- 1 and were 
taken from Wilson, 1972a. In addition, the acid-base 
equilibrium reactions for ammonia, reactions 4.44 and 
4.45 (Castellan, 1983), and for carbon dioxide, reac-
tions 4 . 46 and 4.47 (Weast et al., 1985) were taken 
into account in computer simulations. 
2HO- CH =N? HO-CH=NH + HO-CN {4.35) 
2- 0 - CH=N? HCN + HO- + -o-CN (4.36) 
HO- CN - o - CN + Er" pKa=3.46 (4.37) 
fkO 
HO- CN + g+ N~ ... + 00:z (k=6. ox10-
2 > (4.38) 
HO-CN + EkO Nib + 00:z (k=7. 8Xl0-
4
) (4.39) 
EkO 
-o- CN + 7EkO Nib + He~- (k=8.3Xl0 ) (4.40) 
184 
fh-, O 
- o - CN + H. ... Nib + CCb ( k =43 } (4_ 41) 
HO-CN + NR"3 Nf-bCONI-b (k=17 . 8} (4 . 42) 
- o - CN + NH. .. .... NI-b CONH:z (k=9. 6X1 0-- 0 } (4 . 43} 
NB:,, + f-b O NH. .. .... + HO- ( k =6. OXl <r' } (4 . 44) 
N[L, .... + HO- NE-b + I-bO (k=3. 4X10 1 0 } (4 . 45 ) 
CQz + Eh-,0 HCCb - + ~ pKa =6.37 (4.46) 
HCCk.- c0-:,, 2 - + w? pKa =l0 . 25 (4.47) 
An othe r source for the formation o f NE-b was at-
tributed t o hydrolysis of fh-, C=NH and HO- CH =-NH, reac -
ti ons 4 _4 8 and 4.49. Their rates of hydrolysis are 
n ot known but were assumed to be : 10~ drrr' mole- 1 s - 1 ? 
EkC=NH + f-bO Eb C=O + NE-b (4.48) 
HO- CB =NH + EkO ----1? HCO:z H + NE-b (4.49) 
The formation of formaldehyde is predicted by 
r e a c tion 4.48. Figures 4.16 and 4.17 show gas 
chromatograms and mass spectra of aldehydes products 
that were derivat i zed by 2,4- dinitrophenyl-hydrazine 
(DNP) into 2,4- dinitropheny l - hydrazone (DNPH) deriva-
tives. Formaldehyde, acetaldehyde, propionaldehyde and 
185 
1 
a b C 
3 
2 
?> 
O'.l 
C 4 ' 2 .. 6 0 
(1 ? ., 4 
$') 2 
() !> 
a:: 
6 12 
0 6 12 0 6 
12 0 
Time (min) 
grams of DNPH deriv
atives of 
Figure 4.16 . Gas 
chromato
 (b) and 95 (c) kGy
 in 
aldehydes formed a
t 30 (a), 61
 HCN and 0.001 mole of 0.1 mole dm-
3
al-
:g~;ous solutions  DPH; 3. Form
K4Fe(CN)6. Legend
: 1. Solvent; 2 .
m ehyde; 5. Propional
dehyde; 6 . Butyr-
dehyde; 4. Acetald
8ldehyde. 
 identified by gas 
chromatography 
bu~Yraldehyde were
shows the dose 
and mass spectrome
try. Figure 4.18 
e formation of form
aldehyde. The 
dependence of th
ulated 
emical yields of fo
rmation were calc
~adiation ch 2 ; 
0 3 (CihCH0)=2.70X10-
0 
to be : G (HCH0)=9
.10Xl0- ; G
 26X10-3
0 CH0)=7. ? 
G? fhCfkCH0)=2. 09X10-
3 ; G (Cfk (Cfk )2
(C
186 
91 122 
100 8 
~2 
162 163 224 
210 
50 106 
198 
131 281 
~ 
td 266 
Q) 
0... 0 60 100 160 200 250 300 
Q) 
rn 
aj 
m 
....., 199 
0 100 b 
~ 
226 
263 
50 211 
104 
165 
267 
0 
50 100 150 200 250 300 
m/e 
Figure 4 . 17. Electron impact (a) and chemical ioniza-
tion (b) mass spectra of the DNPH fraction formed at 95 
kGy . Molecular weights of DNPH derivatives: Formal -
d e hyde 210; acetaldehyde: 224; propionaldehyde: 238; 
butyraldehyde:252; valeraldehyde : 266 . 
187 
LO 
0 
12.0 
X 
,......, 0 
,..., 
I 
E 8.0 
'O 
., 
0 
E 4.0 
,..., 
0 
I 
u 0.0 
I 0 25 50 75 
L.....J 
Dose ( kGy) 
Figure 4.18. Formation of formaldehyde as a function 
01 dose in aqueous solutions of 0.1 mole dm- 3 HCN and 
0 . 001 mole dm- 3 K4Fe(CN)6. 
A variety of polycarboxylic acids are formed in 
irradiated HCN solutions. Figure 4.19 shows gas 
chromatograms obtained at different doses. Except for 
oxalic acid (peak 1 in Figure 4.19), their concentra-
tions exponentially increased with dose. Figure 4.20 
shows the variation of concentration of oxalic and 
malonic acids with dose. The identifications of poly-
carboxylic acids were confirmed by mass spectrometry 
using electron impact and chemical ionization 
techniques {Figure 4.21) . Table 4.1 summarizes the 
identification type for each carboxylic acid as well as 
their initial radiation chemical yield. 
188 
a 
? 
20 40 
b 
e 
,, 
0 20 40 
~ 7 
C 
0 
4 ? a ,, 
0 20 40 
Time ( min ) 
Figure 4.19. Gas chromatograms of polycarboxylic acids 
methyl esters from HCN - f<...Fe(CN)o mixtures at 30 (a), 
46 (b) and 95 (c) kGy. 1. Oxalic; 3. Malanie; 4. 
Fumaric; 5. Succinic; 6. 1,2 Dimethyl succinic; 7. 
Maleic; 8. Glutaric; 10. Malic; 11. Carboxysuccinic. 
189 
~ ~ ~ 
~ 
X 
X 
4.0 ,... 
~ 4.0 
n n I 
I 
E E 'O 
'0 
., ., 
0 0 
E 2.0 2.0 E ....,, 
,...... ,....., "O 
"O 
?.:; u 0 
0 
.',,! 
0 C: 
~ 0. 0.0 0 
0 75 100 
c 
........ ::E 
D ~ 
Dose ( kGy) 
Figure 4.20. Dose dependance of the formation of 
oxalic and malonic acids in HCN- ~Fe(CN)o mixtures. 
190 
Oxalio methyl e&1ter 
59 119 
.:,t 100 100 ..>t. 
0 0 
.ID.  Cl) Q.. 0..,.  
~ 50 50 Ill 
C-D m
0  
0 
~ 118 105 
100 150 200 50 100 150 
Molonlc methyl eeter 
59 
100 
~ 100 .:1 
0 Q 
Cl) 
Cl. 101 
Cl) 
a.. 
Cl) ., 
~ 50 50 to 0 
C Q'.l ...D..  
0 't 
~ 1.32 101 ~ 
100 150 200 50 100 150 
Moleic methyl ester 
102 
~ 100 172 100 _,., 
g 
59 69 i a.. 145 0.. 
a,; 50 102 50 I 0 C 
CD ID 
113 134 
I 
100 150 200 50 100 150 
m / e m/e 
Figure 4.21. Electron impact (left) and chemical 
ionization (right) mass spectra of polycarboxylic 
acids formed at 95 kGy. 
191 
Table 4 . 1 . In i tial chemical yields (GD) of formation 
of p o lycarboxylic acids . 
Acid Identificat i on GD 
type* 
Oxa lic ,6 D ... 2 ... ?? 
2.34X10-
Malanie 4 D ? 
Fumar i c ~ D ......  
2.24Xl0-
Succ in ic D ??  
 3 . 39Xl0-15 
D. . 61Xl0-15 
1 , 2 - Dime thyl succinic 6 D ... 
6
<Xl0- 0 
Ma l e i c ? !::. D  5.36Xl0-15 
Glutaric 
? ? 
L:, D ? 8 . 44Xl0-
15 
Adipic ..6 D 3.57X10-0 
Ma li c 0 6. D ... 4 . 99Xl0-
Pime li c ~ D <Xl0-0 
Carboxysucc in ic L:, D ... 4.56X10- 0 
* Re tention time ( L:, ); coinjection with standard 
( ? ); el e ctron impact mass spectrometry {A); and 
chemical ionization mass spectrometry ( ? ). 
The existing data is not sufficient for modeling 
the formation of polycarboxylic acids in HCN solutions 
expos ed to irradiation; however, reactions 4.50 to 4.54 
were included in the simulation to account for the 
f o rma tion of oxamide and/or oxalic acid. The kinetic 
dat a were taken from Behar (1974) and/or Buchler et al . 
( 1976) . 
-- -- -- ------------~ 
192 
HO-C=NH pK =10.2 (4.50) 
HO- C=NH ---+ - CONH2 k =4X107 s - 1 (4.51) 
2?CONH2 ---+ ( CONfk )2 k =3.1X10'9 dm3 mole- 1 s - 1 (4 .52 ) 
H-+-
- o - c =~ ,-.-_--_+  - o - C=NH ? O=C-Nft (4.53) 
2EkO 
2 O=C- NH- --+ {CONH:z)2 + 2HO-
{4.54) 
Oligomeric material was formed in low yield in 
HCN mixtures containing K.,..Fe{CN)6. Figure 4.22 shows 
the formation of this material as a function of dose. 
Its yield increases exponentially as a function of 
dose; the initial chemical yields of formation for this 
0 
material were determined to be: G {C)=l.22; 
G 0 {N)=l.06; G 0 {H)=l.85; and G
0 {0)=0.84. Its origin 
may be explained by successive oligomerization reac-
tions of the radicals previously described (generically 
refereed as X-) with HCN molecules, reaction 4.55. 
X? 
X? + nHCN Oligomeric material (4.55) 
193 
,..-,- .. 2 .0 
I 
E a 
T.1 
(1l 
..._, 
II) 
::, 
"U 
?a; 
(U 
L.. 
c 0.0 
0 0 25 50 75 100 
....--. 
tr) 
I 
E 
"U 0.4 
b 
C7) 
........, 
V 
a> 0.2 
:J 
"U 
'in 
(J) 
I,... -- -- -CT 
c -- -- -B--- -EJ- -- -- --0. 
0 0 25 50 75 100 
Dose ( kGy) 
Figure 4 . 22. Dose dependance for the formation of 
oligomeric material measured as total dry residue {a) 
and as specific elemental composition in the residue 
(b). Legend for b: Carbon ( 0 ); nitrogen ( ~ ); 
hydroge n ( D ); and oxygen ( 7 ). 
Figure 4.23 shows the effect of the concentration 
of hexacyanoferrate(II) on the free radical oligomeri -
zation of HCN. The amount of HCN decomposed is only 
194 
""' 0.06...----------------~ 
n 
I 
E 
"O 
Cl 
0 
E 
......... 
.--, 
z 
u 
.I._ . 
I 0.02-+--+-t' - --~--------r---------j 
0 
Figure 4.23. Dependance of the decomposition of HCN 
as a function of the concentration of ~Fe(CN)o in 
aqueous solutions of 0.1 mole dm- 3 HCN that have been 
expos e d to a dose of 61 kGy. 
markedly decreased at high concentrations of Fe(CN)o 4 -
Figure 4.24 shows gas 
chromatograms of a variety of polycarboxylic acids that 
are synthesized. Their yields are only markedly 
decreased at high concentrations (10-3 mole dm- 3 ) of 
Fe(CN)o 4 - but are not significantly affected at con-
centrations 210-4 mole dm- 3 (Figure 4 . 24). 
195 
0 1 J 7 C 
G) 
II) 
C. 
0 
a 
1/) II 
(I) 
a::: 11 
10 ,2 
0 20 4-0 0 20 40 
I J 7 b I J 7 11 d 
G.) 
Ul 
C 6 
0 
Q_ 
Ill 
(U 
a::: 
0 20 40 0 20 40 
Time ( min ) Time (min) 
Figure 4.24. Gas chromatograms of polycarboxylic acids 
formed in the b' - irradiation of an aqueous solution of 
0 . 1 mole dm- 3 HCN and K4Fe{CN)6 that have been exposed 
61 kGy . The concentration of K4Fe {CN)6 was set to 
{mole dm- 3 ): 1X10-3 {a); 1X10-4 (b); 1Xl0-
6 (c); and no 
additive {d). 
Based on the previous discussion it is evident 
that the effect of hexacyanoferrate{II) on the free -
radical oligomerization of HCN was only its inhibition. 
No new synthetic pathways nor enhancement in prcxlucts 
yields was influenced by the reactions of hexacyanofer-
rate{II) with the free- radicals produced from BCN. On 
the contrary, bexacyanoferrate{II) only led to the re-
formation of BCN by its reaction with the radicals: 
196 
HO- CH =N? and -o- CH=N? (reactions 4.32 and 4.34). 
Therefore, in contradiction to the general ideas of 
the possible catalytic role of cyanocomplexes in 
chemical evolution (Beck, 1978), it seems reasonable to 
conclude that hexacyanoferrate(II) did not play a role 
in the oligomerization of HCN via free-radicals. 
The next section examines the effect of hexacyano-
ferrate(III) on the free-radical oligomerization of 
HCN. 
4.4 The ~-irradiation of aqueous hexacyano-
ferrate(III)-BCN mixtures 
Aqueous, oxygen-free solutions (pff.::i 6) o:f 0.1 mole 
dm?- :s HCN and 0. 001 mole dm- 3 K:sFe(CN)6 were irradiated 
with 6 ?Co-d-rays in a wide dose range up to about 100 
kGy. 
Figure 4.25 shows the decomposition of HCN as 
function of dose. The initial radiation chemical yield 
of decomposition of HCN was determined to be 2.00. 
This value is considerably smaller than that obtained 
197 
0.12~------ ---------
I") 
I ([) ??? ?? ?Q .... . Q 
E ?? ???? .. Q ..... .P .. . "O O.OB ?? ? ?? 
I) 
0 
E 
0 .04 
.--, 
z 
u 
I 
'--' 0.00+---------------~ 
0 25 50 75 100 
Do:1e ( kGy) 
Figure 4.25. Decomposition of HCN in solutions of 
HCN and K~Fe(CN}6. Dotted line was obtained by com-
puter simulation {see text for details}. 
in pure aqueous HCN solutions {G 0 =7.60}. 
The predicted rate decomposition of HCN {dotted 
line in figure 4 . 25} is consistent with experimental 
results. Modeling of this system was carried out taken 
into account reactions 1 to 54 given in Tables 2.3 to 
2.7 {Chapter 2, section 2.7) as well as reactions 4.2 
to 4 . 54 considered in sections 4.2 and 4.3 in this 
chapter. 
The decomposition of HCN was attributed to reac-
tions 4.24 to 4.31. A possible reaction {4.56) of 
198 
hexacyanoferrate(III) with EkC=N? radicals could ac-
count for the marked decreased of G 0 {-HCN) in this 
system: 
EbC=N? + Fe(CN)o 3 - Fe(CN)o 4 - + H~ + HCN {4.56) 
This reaction was included in computer modeling in 
order to derive its rate constant; however, computer 
simulations indicated that such a reaction does not 
participate in the overall reaction mechanism of decom-
position of HCN, and therefore, was ruled out. 
The marked decrease in G 0 ( - HCN) is due to a 
scavenging effect of the species, H? by hexacyanofer-
rate{III): About 64% of hydrogen atoms react with hexa-
cyanoferrate(II) according to reaction 4.18, and 36% 
react with hydrogen cyanide according to reaction 4.24. 
Figure 4.26 shows the decomposition of hexacyano-
ferrate(III) as a function of dose. The radiation 
chemical yield of decomposition of hexacyano-
ferrate(III) was determined to be 0.18. Computed and 
experimental trends agree quite well at low doses 
{<5kGy). Hexacyanoferrate(III) mainly disappears by 
199 
I"') 1.01ar-----------------, 
0 
,--, X 
I .......... 
~ 
.....c..:.o..  I") 
z I 0.5 
u E 
'-" -0 
t.::i 
L . ..J a.> 
0 
E: 
.__, 
0.0 ..-----.-------.-----.-- - ----j 
0 20 40 60 80 
Dose ( kGy ) 
Figure 4.26. Decomposition of hexacyanoferrate(III) 
in solutions of HCN and K"5Fe(CN)o. Dotted line was 
obtained by computer simulation (see text for details. 
reactions 4.18 and 4.19. At higher doses, the computed 
and experimental trends deviate. This might be due to 
reactions of pentacyanoferrate(II) with the free radi -
cals from water radiolysis. 
Figure 4.27 and 4.28 show the experimental dose 
dependence for the formation of hydrogen (G 0 =0.45) and 
predicted formation of hydrogen peroxide (G 0 =0.57), 
respectively. Their mechanism of formation was given 
in detail in Chapter 2, section 2.7, and is summarized 
by reaction 4.1. 
200 
LO 
0 6.D 
X <?-
,,....._ 
I") 
I 4.0 .. -0 
E 
'O CY 
41> 
0 2.0 .D ? 
..E...,  0 
'rN  0.0 
L...J 0.0 0.4 0.8 1.2 
Dose ( l<Gy) 
Figure 4.27. Formation of molecular hydrogen during 
the b' -irradiation of an oxygen-free, aqueous solution 
of 0.1 mole dm- 3 HCN and 0.001 mole dm- 3 K3 Fe(CN)o. 
Dotted line was obtained by computer simulation (see 
text for details). 
v 
.0.. . 4.0 
>< 
,..._ 
n 
I 
E 
-0 
2.0 
~ 
0 
E 
....... 
,...., 
N 
~ 0.0 ? 
r.: 0.0 2.0 4.0 6.0 
1..-1 
Dose ( kGy) 
Figure 4.28. Computer simulation for the formation of 
hydrogen peroxide during the ~-irradiation of an 
3 
oxygen- free, aqueous solution of 0.1 mole dm- HCN and 
0.001 mole dm- 3 ~Fe(CN}o. 
201 
Carbon dioxide (Figure 4.29) and ammonia (Figure 
4.30) are the major products formed from HCN- f6Fe(CN) o 
mixtures. Their initial radiation chemical yields of 
format ion are 1 . 00 and 1.10, respectively. Their 
mec hanism of formation may be explained by reactions 
4.35 and 4 . 36, followed by reactions 4.37 to 4 . 43. In 
addition, ammonia may also formed by hydrolysis of 
IkC=Nfl (reaction 4 . 48) and HO- CH=NH (reaction 4.49) . 
..,. 
0 
X 1.5 
......,_ 
r<') 
I 
E , .o 
"'O 
I) 
0 
E 0.5 ..._,  
,......, 
<'4 
0 o. 
.(....)..  0.0 0.4 0.8 1.2 
Dose ( kGy) 
Figure 4.29. Formation of carbon dioxide during the 'ti-
irradiation of an oxygen-free, aqueous solution of 0.1 
mole dm- 3 HCN and 0.001 mole dm- 3 lbFe(CN)o. Dotted 
line was obtained by computer simulation. 
202 
,,., 
0 
1.5 
X 
...-.. 
I') 
I 1.0 
E 
"O 
~ 
0 
E 0 .5 
......., 
~ 
:  0 . zr 0.0 5.0 10.0 15.0 
L-1 
Dose ( kGy} 
Figure 4.30 . Effect of dose on the concentration of 
ammonia formed radiolytically in 0.1 mole dm- 3 HCN and 
0 . 001 mo l e dm- 3 K3 Fe(CN)o aqueous solutions. 
Figure 4.31 shows gas chromatograms of aldehydes 
formed in the radiolysis of HCN- I6Fe(CN)o mixtures. 
Formaldehyde (G 0 =9.10X10- 3 ), acetaldehyde 
(G 0 =3 . 41X10-2 ); propionaldehyde (G
0 =7.19X10-3 ), and 
butyraldehyde {G 0 =1.75X10- 2 ) were all identified by 
their retention times and coinjection of standards in 
gas chromatography, and also by their fragmentation 
pattern by electron impact and chemical ionization mass 
spectrometry (Figure 4.32). Their radiation chemical 
yields were calculated from the slope of concentration 
vs dose plots as that shown in Figure 4.33. The con-
centration of formaldehyde linearly increase with 
203 
a b C 
2 
Q} 4 
(/) 
C 46 
0 6 
D... 
(/) 2 3 
Q} 5 
Cl'.: 5 2 
0 6 12 0 6 12 0 6 12 
Time (min) 
Figure 4.31. Gas chromatogram of 2,4-dinitrophenyl -
hydrazone derivatives of aldehydes formed at 27 (a), 61 
(b) and 95 (b) kGy of b' - irradiation of an oxygen- free, 
aque ous solution of 0.1 mole dm- 3 HCN and 0.001 mole 
dm- 3 K3 Fe(CN)6. See legend in Figure 4.16 for peak 
assignment . 
irradiation dose. Its mechanism of formation may be 
e x p lained by reaction 4.48. 
204 
a 11 1112 JOO ... 
ao lOtl 
.!?II  
P"-.  0 lid1tt 60 lOO t6D 200 2110 300 
Al 
?IQ 
.p
 
..:.i  un 
0 100 b a,a 
a( 
111 
1DO -
atw 
0 
M 100 l!W 800 2ffO 300 
m/e 
Figure 4.32. Electron impact {a) and chemical ioniza-
tion {b) mass spectra of the 2,4- dinitrophenyl - hydra -
zone fract ion formed at 95 kGy in the HCN- K"" Fe(CN)o 
sy s t e m. 
IJ') 
0 
>< 12.0 
I') 0 
I 
E 8 .0 
"U 
CV 
ci 
E '4-.0 
....., 
,---, 
0 
I 
u 0.0 
:r: 0 25 50 75 100 
L.......l 
Dose ( kGy) 
Figure 4 . 33. Dose dependence for the formation of for -
maldehyde in the HCN - K:sFe(CN)o system. 
205 
Oxalic acid was identified as the major polycar-
boxylic acid formed in irradiated HCN-KsFe(CN).,, solu-
tions (F igure 4.34). A variety of other acids were 
, 0 
e 
.. ,o,, 
0 20 40 
b 
~ 
C CJ 
0 
a_ 7 
In 
CV 
a::: 
? 11 
0 20 4-0 
3 7 C 
0 
Time (min) 
Figure 4 . 34. Gas chromatograms of polycarboxylic acids 
methyl esters formed at 27 {a), 46 {b) and 95 {c) kGy 
in the HCN - K3 Fe{CN).,, system. See Figure 4.19 for peak 
assignment . 
206 
also formed but in low yield. Their identification was 
based on retention times and coinjections with stan-
dards in gas chromatography. Supporting evidence was 
based on the GC-MS analysis carried out for the HCN-
K...Fe(CN)6 system (Section 4.3). 
Table 4.2 summarizes the initial radiation chemi -
cal yields of formation of polycarboxylic acids. 
0
Table 4.2. Initial chemical yields (G ) of formation 
of polycarboxylic acids. 
Compound 
2 
Oxalic l.60X10-
4 
Malonic 1.1sx10-
Fumaric 3.90X10-!5 
Succinic 2.57X1Q-!5 
1,2- Dimethyl succinic 9.95Xl0-
6 
Maleic l.14Xl0-
4 
Glutaric 2.83X10-!5 
Adipic 5. 12Xl0-
6 
Malic 5.87Xl0-
6 
207 
The con c entrat ion of polycarboxylic acids exponentially 
i n c r e ases wi th dose with the exce ption of oxalic acid . 
Figure 4 . 3 5 s h ows these b e h a v i or f or oxa l ic and ma leic 
acid s. 
?0  ~ 
r 
X X 
~.o 4.0 
~ n 
I I 
[ E 
~ ~ 
C w 
0 0 
E 2.0 E 
~ 
u ~
~ u 
 
0 0 
~ ~ 
0 0. 0 .0 ~ 
.~.... . 25 50 75 100 ! 
D 4 
~~ (~) 
Fig ure 4.35. Dose dependance of the formation of 
oxali c and maleic acids in the HCN - KsFe(CN)6 system. 
Oligomeric material was formed in low yield in 
HCN- K3 Fe{CN)6 mixtures (Figure 4.36). At low doses its 
is very low but exponentially increases with irradia-
tion dos e . The initial radiation chemical yields of 
208 
formation for this materia l we r e determined to b e: G 0 
{C) =0 . 87; G 0 (N) =0.82; G 0 (H) =0.88; and G 0 {0) =0.09. 
,......_ 
I") 2 .0 
I 
E. a 
u 
Q\ 
'-./ 
1.0 _____,-9-
(IJ 
::, 
u 
' in D~ 
Q) e? ~ 
~ 
c 
0 0 .0 0 25 50 75 100 
,--. 
I") 
I I 
r 0.4 b 
'O ' 
c,, 
......, 
Cl) 
::, 
"C 
'in 
.Q..J.  
?:-
0 0 2b 50 
Dose ( kGy) 
Figure 4.36. Dose dependance of the formation of 
oligomeric material measured as total dry residue {a) 
and as specific elemental composition in the residue 
(b): Carbon { 0 ); nitrogen ( 6 ); hydrogen ( D ); and 
oxygen ( 7 ) . 
209 
The results given in this section indicate that 
h exacyanoferrate(III) does not lead to an enhancement 
o f p r oducts yields nor contribute to new synthet ic 
pathwa y s . Hexacyanoferrate(III) markedly inhibits the 
d ecomposition and oligomerization of hydrogen cyanide . 
The mechanism responsible for such an effect is due to 
the s c avenging of H- and e..q by hexacyanoferrate(III), 
r eactions 4 . 18 and 4.19. Therefore, it seems 
r easonable to conclude that hexacyanoferrate(II) did 
not play a role in the oligomerization of HCN via free -
radicals . 
A comparison of the results obtained in the radio-
lysis of hydrogen cyanide in the presence or absence of 
h exac yanoferrate(II) or (III) is given in section 4.4 . 
210 
4.5 The effect of cyanocomplexes in the free-radical 
oligomerization of BCN: Implications to chemical 
evolution 
Tabl e 4 . 3 summarizes the initi a l radiation chem i -
c a l yields of major produc ts obtained in the radiolys is 
of aqueous solutions of 0.1 mole dm- 3 HCN in the 
Table 4.3. Initial radiation chemical yields (G
0
). 
Compound Go 
HCN 
No additive K. .. Fe( CN )b ~Fe(CN)6 
-HCN 7.60 2.00 2.00 
F'e( CN ) 6 3 - 4. 10 - 0.18 
Ek 0. 3S- 0.45 0.45 
CO:z 0. 80- 0.60 1.00 
Nlb 2. 4?>- 1.01 1.10 
HCHO 0. 18 0.009 0.009 
( COzH) 0.22 0.022 0.016 
Oligomeric 
material: ( - HCN) 5.80 1. 22 0.87 
-nraganic et al., 1973. 
211 
absence or presence of 0.001 mole dm- 3 of ~Fe(CN) 0 or 
f6 Fe(CN)o. 
The decomposition of hydrogen cyanide is markedly 
dec reas e from 7.60 to 2.00 in the presence of hexa-
cyanoferrates. Carbon dioxide and ammonia were the 
major products in the presence of cyanocomplexes. The 
yi elds o f othe r products such as formaldehyde and 
oxalic acid were decreased at least by an order of 
mag nitude . About 76% of decomposed HCN molecules are 
bu i lt up into larger molecules in pure HCN solutions. 
The yield of this oligomeric material decreases to 
about 61% or 44% in the presence of hexacyanofer-
rate (II) or (III), respectively. 
The effect of hexacyanoferrate(II) or (III} on the 
radiolysis of aqueous solutions of HCN was the marked 
decrease in the yield of decomposition of HCN. In the 
case of hexacyanoferrate{II), this effect was 
attributed to the re-formation of HCN by the reactions 
of Fe{CN)o 4 - with HO- CH=N? and - o - CH=N? , reactions 4.32 
and 4.34: 
212 
HO- CU =N? + Fe(CN)6 4 - --+ Fe{CN)6 3 - + HCN + HO- {4.32) 
- o - CH =N? + Fe{CN)o 4 - --+ Fe{CN)o 3 - +HO-+ - cN (4 . 34) 
Whereas in the case of hexacyanoferrate(III), the 
ma rke d decreas e in G 0 ( - HCN) was attributed to a 
scav e ngin~ effect of H? by hexacyanoferrate(III): 64% 
of hydrogen atoms react with hexacyanoferrate{II) ac-
cording to reaction 4.18, and 36% react with hydrogen 
cyanide according to reaction 4.24. 
4
---t_ _: Fe(CN)6 - + w? {4.191:1) H? F e (CN) a 3 -
Fe(CNh, 3 - + HCN {4.19b) 
H? + HCN I-bC=N? {4.24) 
In spite of the differences in mechanisms between 
hexacyanoferrate(II) and (III), the overall effect is 
the same, a marked decrease in G
0 ( - HCN). Furthermore, 
the initial yields of certain products such as H:.z, NH3 
and HCHO are almost similar, and at higher doses of ir-
radiations the differences in product yields becomes 
less apparent between the two systems (see for instance 
GC profiles for carboxylic acids, Figures 4.19 and 
4. 34). The lack of a significant difference between 
the two systems, particularly at high doses, is due to 
213 
the fast interconversion of hexacyanoferrate(II) into 
(III) and viceversa. Therefore, after a few Gy of 
radiation dose, both hexacyanoferrate(II) and {III) are 
participating in the reaction mechanism. 
The effect of other cyanocomplexes of transition 
elements on the free- radical oligomerization of HCN is 
expected to be similar to that found for hexacyanofer-
rate(II) and (III). This is because the rates and 
modes of reactions of cyanocomplexes of transition 
elements with hydroxyl radicals (Figure 4.37), hydrogen 
atoms (Figure 4.38), and hydrated electrons (Figure 
4.39) are very similar. 
214 
,,......._, 11 
10 
-r--
I 
(/) Pi(II) 
9 tvlo( IV) Os(II) Fe(II) 
.- 10 g 0 0 
I 0 0 
(I) Ru(II) Ni(II) Au(!) 
0 
E 5 10 
t'1 
E 
'U 3 
....._.,. 10 
~ 
1 2 3 4 5 6 7 8 9 10 
Number of d electrons 
Figure 4.37. Dependance of the rate of reaction {k) of 
hydroxyl radicals with cyanocomplexes of transition 
eleme nts. Values were taken from Ross and Ross, 1977, 
and Buxton et al . , 1988 . 
215 
, 1 
---- 10 ,--
I 
rt) Ni( II ) 
9 Fe(III) 
0 
,-- 10 0 
I 
-Cl) 
0 
5 0 Pt(II) 
Cd(II) 
E 10 Co(III) 
n 
E 
-0 3 
....__ 10 
_y 
1 2 3 4 5 6 7 8 9 10 
Number of d electrons 
Figure 4.38. Dependance of the rate of reaction (k) of 
hydrogen atoms with cyanocomplexes of transition ele-
ments. Values were taken from Anbar and Ross, 1975, 
and Buxton et al., 1988. 
216 
11 
..-.... 
10 
r-
fl) Mn(II) Co(ll) 
g Hg(l i) Mo(IV) Ni(II) Au(I) 
,--- 10 0 Fe(III) 0 0 
I Cr(l11) 0 0 
-Q) Cr(II) Co(III) 0~ 
0 Pd(II) 
5 0 Cd(II) E 10 Pt(II) Cu(I) 0 
Zn(II) 
r<) 
[ 
TI J 
..,___, 10 
..:::L. 
1 2 3 4 5 6 7 8 9 10 
Number of d electrons 
Figure 4.39. Dependance of the rate of reaction (k) of 
hydra~~d electrons with cyanocomplexes of transition 
elements. Values were taken from Anbar et al., 1973, 
Ross, 1975, and Buxton et al., 1988 . 
217 
4.6 Conclusions 
A comprehensive investigation of the effect of 
hexacyanoferrate(II) and (III) on the free-radical 
oligomerization of HCN was carried out. The t - radio-
lysjs of aqueous solutions of 0.02 mole dm- 3 K4Fe(CN) 6 , 
0.1 mole dm- 3 HCN in the presence of (10-~-10-3 mole 
dm- 3 K4Fe(CN)o or 10-3 ) K~Fe(CN)o were investigated in 
a wide dose range. 
The radiation chemical yields for a variety of 
products were calculated, these included among others: 
fb, C<b, NE-6, Fe(CN)o 3 - , Fe(CN)o4- , and a variety of 
aldehydes and polycarboxylic acids. 
The results indicated that hexacyanoferrate(II) or 
{III) have a significant effect on the free-radical 
oligomerization of HCN; however, rather than increasing 
the product yields and/or opening new synthetic path-
ways, re-formation of HCN, and predominant production 
of CO::z and NE-6 were the principal pathways. 
Computer simulations were performed to model the 
radiolysis of mixtures of aqueous solutions of hydrogen 
cyanide and hexacyanoferrates. The reaction mechanism 
consisted of about 110 simultaneous chemical equations. 
218 
Evaluation of the experimental data by computer 
simulation permitted the elucidation of the mechanism 
and the d e rivation of the rate for the followine reac-
"Lions: 
HO- CH =N? + F'e(CN) 6 4 --+ Fe(CN)6 '3- + HCN + Em-
- o - CH=N? + Fe(CN)o 4 - ---+ Fe(CN)o 3 - + HO- -f - cN 
Th e results obtained 1.n this study provide an 
insight into the possible role of cyanocomplexes in 
chem ical evolution. 
219 
CHAPTER 5 
GENERAL CONCLUSIONS 
Hydrogen cyanide is generally considered to have 
b een a k e y molecule in the process of chemical evolu-
tion becaus e : 
1 . It is widely distributed in the interstel -
lar medium, in the comets, and in the 
atmospheres of Jupiter and Titan; 
2. It is readily synthesized under a large 
variety or experimental conditions that are 
relevant to primitive Earth scenarios; and 
3. It is an important precursor to the 
synthesis of a large array of biomolecules. 
The extensive literature on the abiotic chemistry 
of hydrogen cyanide was reviewed in Chapter 1. At 
220 
present, the re is a significant understanding of several 
asp ects of the abiotic chem i stry of hydrogen cyanide. 
The r e were two are a s of r esearch, howe ver that r e quired 
fu r ther si.,udy: 
1 . Th e invest i g a t ion o f tb P. e l ectros ynthes i s of 
hydrogen cyanide from a simulated primitive 
atmosphere; anrl, 
2. The p os s i bl e rol e of cyanocomplexes of tran-
sition metal ions on the free - radical 
oligomeri z ation of hydrogen cyanide. 
The main researc h objec tive of this disse rtation 
was a compre h e n s ive investigation into the chemistry of 
hydrogen cyan ide. Although much work has been done in 
th is f ie ld, it has been of a qualitative nature. To 
obtain a better understanding, we have concentrated on 
the quantitat ive and modeling aspects as well . 
221 
5 . 1 Electrolysis of a simulated primitive atmosphere: 
The synthes i s of hydrogen cyanide. 
5 . 1 . 1 Quantitative methods 
Three new methods were developed to determine the 
preci s e dose rate supplied by high voltage, high fre -
que n c y electric discharges : 
1. Using methane as the chemical dosimeter; 
2 . Measurements of the electric discharge vol -
tage and current through an oscilloscope; 
and, 
3. Measurements of the electric discharge vol -
tage and current by calorimetry . 
The dose rate was determined to be 2 . 73 MGy hr-
1 
with a standard deviation of 15%. Knowledge of this 
parameter was essential to study the electrolysis of a 
simulated primitive atmosphere . 
222 
5.1.2 Quantitative results 
Th e cle<:t.ro lysis of a CH ... - N2-EhO gas mixture wa ::c; 
-Lhoroughl y i nvestigated: 
1. The initial chemical yields of decomposi-Lion 
of me thane and nitrogen were determined to 
be 6 . 54 and 1 .26, respectively . 
2. About 96% of the initial methane and 10% of 
the initial nitrogen were converted into: 
a . C2Eh (G 0 =2.14); 
b. C2Ho (G 0 =0. 57); 
C. HCN (G 0 =0.26); 
d . CH:'S CHO (G 0 =0. 13); 
e. CH3 CfhCHO (G 0 =0. 011); 
f. Cih(CEh)2CHO (G 0 =0.016); and 
g_ Unidentified water- insoluble oligomeric 
material (G 0 =0 .25 for carbon). 
5.1.3 Computer modeling 
A free radical mechanism was developed to account 
for the chemical changes produced by electric dischar-
ges. Computer modeling of such a mechanism could ef-
223 
ely predict the initial trends 
of experimental 
fectiv
data . 
1. Hydrogen cyanide originated
 according to the 
following mechanism: 
Cfh? + ?N: HCN + E:b 
:C~ + ?N: HCN + H? 
Computer modeling of this system
 permitted 
2. 
an evaluation of the possible ra
te of 
production of hydrogen cyanide 
in the primi -
tive atmosphere under a variety
 of condi-
tions such as chemical composit
ion, pres-
0 
ure, and temperature. G {HCN) 
could vary 
s
from 0.1 to 0.4 depending on the
 atmospheric 
conditions. 
 of HCN 
3. The possible rate of electro
synthesis
o 
in the primitive atmosphere was 
estimated t
3 3 y- 1 
vary from 10-4 to 10- mole cm-
s. 
depending on the atmospheric co
ndition
224 
5.2 The effect of cyanocomplexes on the free-radical 
oligomerization of hydrogen cyanide 
Cyanocomplexes of transit i on elements are general -
ly believed to have played a role in the catalysis and 
synthesis of biomolecules in the process of chemical 
evolution. The main research goal was to investigate 
the possible effect of cyanocomplexes of transition 
eleme nts on the free - radical oligomerization of HCN . 
Specifically, we were interested in hexacyanoferrate 
(II) and (III), sinc e they probably accumulated in the 
primitive oceans. There was great interest in this 
invest igation since only a limited number of studies in 
abiotic chemistry has been devoted to examine the ef-
fec ts of metal ions in catalyzing reactions of 
sign i ficance to the origins of life. 
A comprehensive investigation was undertaken to 
study the ~- irradiation of aqueous solutions of 
hydrogen cyanide in the presence of hexacyanofer-
rate(II) or (III) . 
5.2 . 1 Radiation chemical yields 
The G 0 values for HCN, JC..Fe{CN)6 , K:sFe{CN)6, Eb , 
CO:z, HCHO, CibCHO, ClbCEbCHO, Cib{CEb)3 CHO, {C<:kH)2 and 
225 
a v a riety of polycarboxylic acids were determined und e r 
different conditions. 
5.2.2 Mechanism of reaction 
Evaluation of the experimental data by computer 
simulation s consisted of about 110 simultaneous chemi -
cal reactions . This study permitted the elucidation of 
the rea ction mechanism: 
1. Hexacyanoferrate(II) reacts with HO- CH=N? 
and/or - o - CH =N? according to : 
HO- CH =N? + Fe (CN)o 4 - ---+ Fe(CN)o 3 - + HCN + Ho--
- o - CH=N? + Fe (CN) o 4 - ---+ Fe(CN)o 3 - +Ho- + - cN 
2. He xac yanoferrate (III) competes with hydroge n 
cyanide for hydrogen atoms . 64% of hydrogen 
atoms react with hexacyanoferrate(II) ac-
cording to: 
Fe(CN)o 4 - + w-
H- 3
+ Fe(CN)o - ~-- -: Fe( CN b 3 - + HCN 
H? + HCN fkC=N? 
2?o 
5.2.3 Effect on the free - rad ical oligomerization 
of HCN 
Th e dec omposition of hydrogen c yanide was markedly 
decrease from 7.60 to 2.00 in the presence of hexa-
cyano:ferrat.es . Carbon dioxide and ammonia were the 
major products in the presence of hexacyanoferrates. 
About 76% of decomposed HCN molec ules are built up into 
larger mo lec ules in pure aqueous HCN solutions. The 
yield of this oligomeric material d ecreases to about 
61% or 44% in the presence of hexacyanoferrate(II) or 
(III), respectively. The results obtained in this 
study provided an insight into the possible role of 
cyanocomplexes 1n chemical evolution. 
2 2 7 
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CURRICOLUM VITAE 
Name? Rafae l Navarro - Gon z ~lez 
Permanent address: Inst i t uto d e Ci e n c ias Nucleares , 
Uni v ersidad Nc1cional Aut,onoma d e 
Mex ico, Ciudad Universitaria, 
Mex ico D.F. 04.510 MEXICO 
lJl:/; ret: aTJd d at,e Lo h e conferred: Ph.D., 1989 
DuLc? uf hiri ,h: April 25, 195 9 
PJace of birth : Me xico, D. F., Mexico 
Col lcr;iai.,e lnstituL.ior is attended: 
D/\TE OF DEGREE 
Onjvcr:.,; jt,y of' Maryland , Collet;e Park 
1984- 1989 Ph.D . 1989 
Biuc bemisLry 
tJniVf )Y-;,jdad Nac iona] Autonoma de Me xico, Me xico City 
1978 - 1981 B. Sci. 1983 
Bi o logy 
llonor~;: 
1 . 1980- 1982. Research Fellowship from Th e Nationa] 
Autonomo us University of Mexico. 
2. 1984- 1989. Researc h F e llowship from Th e National 
Autonomous University of Me xi c0. 
Me mbe rsb.ips: 
1. International Soc iety for the Study of Origins of 
life . Associate Me mbe r, 1981 -
2. Mex ican Chemical Society. Member, 1986-
3. Radiation Researc h Society. Student Member, 1986-
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zal ez, R . and Vujosevi c , S . I . (1 987) . Tb e 
P r esenc e o f Polyme ri c Material in Radi o lysed A-
que ous S o lutions of Ammo n i um Bicarbona t e. Rad j~~~ 
Ph s . Che m. 30, 229 - 2 3 1 . 
8 . Na v a rro- Gonzal ez, R ., Ne gron - Me ndoza , A., Chaco n, 
E. and Honda, Y. (1989) . Th e ~-Rad iolysis o f 
Aqueou s So lutions of Urea. Implications for 
Ch e mica l Evolution. R~d t at . Phys. Chem. (in 
press ). 
9. Honda, Y., Ni:ivarro Gon za l e:-:, R. and Ponnamperuma, 
C. ( 1989). Cbf~roica] Yje]d s of Biologjcally Impor -
i.,1-rni, rorrJ1,our1ds f1l)r11 l~J ec.: Lrjc : Djscharges . .Radiat . 
fh_ys_. __ .C.b~n;i . ( in prPs :_.; ) . 
10 . Honda, Y. , Navar ro - Gm 1:,-.6lez , R. and Ponnamperuma , 
C . ( 18B 9 ). A Qu an-t i 1 nt, i v e Assay of Bioloe;ically 
Important, Comp(nrnd:; in ~~i mu l c1tFid .Pr irui ti v e ? artb 
I!:xpe r iru rm Ls . Advan ces in S~ace Research ( in 
pre~;~). 
11 . N,w arro- Gon7.~ l f'1/., R . , Neg re n - MP.ndo6a , A. , A1;u i rre 
Ca J d e r on, M. E . , aod Ponnrl mpe rum u , C. ( 1989). Th e 
- Irradjat.,jon o f Hyrlroc r.n Cyc1njde jr, thP. Presence 
of F errocyc1nide or VP.rricyanidc. Implications to 
PP~lii oL.il? Chcmi:;t r?y. Ad y,m cl:~~- in $p ;cw~t R~~Qgn:!h 
( lll Prl?SS ). 
1~. Nava r-ro-Gon:6illez, R . , Negr6n - Me rn..loza, A. and 
Cha c6r1, E. ( HJR9). Th e : - Irn1Ji11Lion oC Aqueou s 
Snlu1Jious of Uren.. Tmpl i ca t,jons for Chemical 
Ev u ]uL iun . Origjnci _uf L:ife and Evo]ut, ion of th e 
Biosn_b_~r~ ( in press ). 
11 . Na v a rro - Gcmz.:i l e:;: , R. and P onnamperurn11, C. Th e 
Mechani sm of Bacter i a l Luminescence (Spa nish) 
(1989 ). J. Me x:ican...Sh E-:m. Soc. (in press ). 
1-1. N~i:1 ron - Mr.nd o:-: c1, A . , and Navarro - Go n z.:i 1 ez, R. Th (: 
~- Irradiation of Aqu eous Acetic Acid - Clay suspen-
sions. Subm i tted to Radiation Effects . 
15. Navarro- GonzJ.l ez , R. and Negr6n- Mendoza, A. 
Microdetermination of Formic Acid. Submitted to 
J_ __,__lkx_j (!gl)_ ~p ql._yt,icn l Ctg;~_!Jl_,_ Soc . 
16 . Navarro-Gon z ~l P-7. , R., Honda , Y., and PonnampP-ruma, 
C. Dosimetry of High Voltages Electri c Dischar-
ges. ln preparation. 
Contributions presente d at Scientific Meetings: 
1 . Navarro-Gonz~ l ez, R., Negron - Mendoza, A. , 
Draganic, Z. and Dragan ic, I. (1982) . Car-
boxylic Acids and Carbonyl Compounds Formed 
Radiolytically in Aqueous Solut,ions of Nitriles 
(Spani sh } . Abst,T~cts for the IVS mposi um on 
.Nu cJ ~a r Ch em~ s Lry, Rad :i,och emi?:tIT_i!_nd Radiat_i_9_n 
Ch e mistry _ U.N.A.M .? Mexico. p . 33. 
2 . Ne gr6n - Me ndoz5, A. , Navarro- GonzA l ez, R., 
Drae;anic, Z. and Draganic, T. (198 2 ) . Carhoxylic 
Aeids and Carbonyl Compo und s Formed Radiolytica lly 
in Aqueous Solut, ions of' Cyan i d es (Spanish). 
Abstnic t,s for the IV .QY[OJ)Qsium on Nuclear 
~hr:rn :i ~t, ry ,.__ Hr1rl :i. ocheroi st,r and Radiation _Ch ~rr1 i.fit.r~ 
U. N. A.M . .._ Me xico. p . 34. 
3 Na vc1 r ro- Gon~Jez, R., Negron- Me ndoza, A., Torr es, 
J.L., and Ponnamperuma, C. (1986 ) . The Effect of 
Some Cyanocomplexe s of Transition Elements in t,hc 
Radluly sis of Hydrogen Cyanide. I. Iron (Spanish). 
Abstracts for the VJ__fu.J!!.Qosium on Nuclear 
Ch e mistr..Y.._ Ra_d j ochemistr and Radiation Cb~I!Ji.str~ 
Pu e hJ_a,_ _ Mexjco, Dec. 1- 5. 
4 . Navarro- Gonzalez, R. and Ne g-ron - Mendoza , A ( 1986) . 
Products from th e Decomposition of Methane under 
dif'ferent, En e r g y Sources (Spanish) . Abstraqts for 
.tb e VI Symposium on Nuclear Ch emisj_-_,__ry_,_ 
R,~d i od1emj st01 and _Rml i at ion Ch e mist r..Y..,__ Pue bl g, 
Me xi c g_,_J)..J=c . 1 - 5. 
5. Honda, Y., Navarro- Gon~lez , R . and Pormamperuma, 
C. (1988). Dosimetry of Electri c Discharge Ex -
periment~; in Che mi ca l Evolution . Abstract~,_f(J_:[ 
the Thir.t.Y :--Sixth Annual Meet in of th e Radi ation 
RP.search SoQiety_ Philadel..Qhi a , PA . p . 144. 
6 . NRvarro - Gonzalez , R., Negron- Me ndoza, A. and 
Ponnamperuma, C. (1988). b-Radiolysis of Hydrogen 
Cyanide in tb e Presence of Cyanocomplexes. Im-
plications f'or Chemical Evolution. Abstracts for 
.t.be Thirt - Sixth Annual Meetin of the Radiation 
1-lf~secirch Society . Phjlad e l_Iili.i ;:i, PA. p . J4 9. 
7. Honda, Y., Navarro- Gonz~lez, R . and Ponnamperumr1, 
C. {1988 ). A Quantitative Assay of Biologically 
Important Co mpounds in Simulated Primitive Ear~h 
Experiments. hbstracts from the XlVII Plenar 
.M-~ ~_t_;in_g_ _ of _U H~ S.Q~_UJ:i ~t~_!LQn ~ce Resear ch_.._ _E?:..2.00 , 
Finland, July 18- 29. p. 383. 
U. Navcirro- GonzAJ ez , R . , Negrdn - Me ndoza. A., Aguirre -
Calderon, M.E . . and Ponnamperuma, C. {1988). Th e 
~-Radiolysis of Hydrogen Cyanide in the Presence 
of Ferro- and Ferricyanide. Implications to 
Prebjotic Ch e mistry. Abstracts from the XXVII 
Elenar Meeting of the Committee on S ace 
Es oo, Finlapd, July 18- 29 . p. 38 3. 
!J . Na v a rro -GonzA) f?Z, R., Negron - Me ndoza, A . , Ctrncon, 
E arid Hnn,la, Y. (19 88 ). Th e ?? - Radiolysis of 
/~queous Solutions of Ure u . Implications for 
Ch P-rni ca J b:v o l uti on. Abst,ra c i, s __ from -tbe _VII Sy~--
p os ium _oo Nu c lear Ch e mls1.,r:,y Radiochemist :ry _ and 
.l<~d :j_ at, i QJ;:l ..(.;h~i;n i ?.t.KY..,__Z_~ Q.ateca ~; , Mexico ,__ Ju J _y_ 2 ~ -
%U . 
10. Ilo nd ,1, Y . , Navarro- Gonz.Al ez , R. and Ponnamperuma, 
C . ( J9 8U ). Ch e mical Yj e ]d s of Biologica ]]y Impor -
'tanL Co mpo und'.; .fro m El ectri c Di sch n r~es. 
AlJ~ t ra c ts . from the VI I Syrp_go~i l,!!!!__oQ__Nu c l. e?:r 
Ch c [oj ~t_.r::Y,. _ _F.9.d !QQ.b e m_i ~.:t:r~ ~nd_Fa_Qi 9 1, i mL..C.be mi ~.:1,ry '--
ZacAtecas Mex i c oi July 25 - 29 . 
11 . Na varro - Gom~~J e:,;: , R. and P onnampe rurna C. (1988) . 
HCN ,mcl Biochemi c al Ev o lution . Th e Poss ible Rol e 
of Iron j n Pre Liological Evolu'tion. .l'lH~ Nir_t!.,b 
Virgi_  nia Biochemis ts Mee ting . Airli o, Virginia, 
Oc tolie r '1 - 9, 1988 . 
12. Uond a, Y., Na varro- Gonzale~, R. and Ponnampe rum a , 
C. ( 1988). Studies on Biochemical Evolution. I. 
Quantitative Assay of Biologically Important Com-
pound _; in El e ctric Discharge Experiments . Th e 
N.inU1 Vire;inia Biochemists Me etinc;. Airli e , Vir -
ginia, Oc tobe r 7 - 9, 1988. 
11 . Na varro- Gonzal ez , R., Ne~ron - Mendoz a, A. and Pon-
nampe ruma, C. Clay - Mediated Decarboxylation of 
Acetic Acid. The Role of Radiation Heterogeneous 
Catalysis in Prebiotic Chemistry. To be presented 
at r-h e 9th __ Internat] ona] Cl ay~f~ :ren QQ. Stras -
b o urG, France , August 2 8 , 1989 . 
ProfHssjona) positions h e ld: 
1. 1989- Associate Research Professor. 
Institute of Nuclear Sciences, Univer-
sidad Nacional Autonoma de Mexico. 
2. 1987- 1989. Re search Assistant. Department of 
Ch e mistry. University of Maryland at 
College Park . 
3. 1984- 1986. Teaching Assistant. Department of 
Chemistry. University of Maryland at 
College Park. 
4. 1983- 1 9tM . ]fe:"'. ? --~rcL A:;,:, H' ia te. Cen t,er nf Nuc .leur 
GLw1.iv: , !lr,1vet?sj d ;1d t!:ir : jon r11 
Aut .on umn d e Mr'!xic,.? 
5. 1 9 f: 0 -- 1983 . f(r ! i?; 1. ' <.1 rcb A:, i: i :-~ Lnn-1. C(Jr, LE::r i:1 f Nuclear 
SLudi.e ~,_. Ui,jvpr?; i dac Nr1r ~innhl 
Aut-.r,nom,-1 d r: Mr., JLl.1" 1 '. 
6. 1 98O- J 9f;j . Tea chit1fr Ass j st,ant Ji'a1:u lty r,f ~;r; jen 
Cl'-!'., . Ur,jve r ~; id,,,rj N.:,:ion ,11 Adi.onorrm dr? 
Mt.: xj cu.