Hydrogen atom initiated chemistry

Abstract

H atoms have been created by the photolysis of H2S. These then initiated reactions in mixtures involving acetylene-ammonia-water and ethylene-ammonia-water. In the case of the acetylene system, the products consisted of two amino acids, ethylene and a group of primarily cyclic thio-compounds, but no free sulfur. In the case of the ethylene systems, seven amino acids, including an aromatic one, ethane, free sulfur, and a group of solely linear thio-compounds were produced. Total quantum yields for the production of amino acids were approximately 3 x 10(-5) and approximately 2 x 10(-4) with ethylene and acetylene respectively as carbon substrates. Consideration is given of the mechanism for the formation of some of the products and implications regarding planetary atmosphere chemistry, particularly that of Jupiter, are explored.

Prebiotic formation of ‘energy-rich’ thioesters from glyceraldehyde and N-acetylcysteine

“…Thioester formation only requires relatively simple catalysts that were probably available on the prebiotic Earth. The prebiotic production of imidazole catalysts seems likely, since imidazoles are readily produced by the reaction of sugars, including trioses, with ammonia (Grimmett, 1965;Kort, 1970) and with amidines (Ames, 1957 conditions (Sagan and Khare, 1971 ;Hong and Becker, 1979). The observation that the rate of lactate formation in the absence of thiol with imidazole exceeds that with phosphate, suggests that chemical energy might be obtained without thiol from glyceraldehyde in imidazole solutions by rearrangement of the carbinolamine adduct of pyruvaldehyde and imidazole to give N-lactoylimidazole, an 'energy-rich' acylimidazole (Jencks, 1976).…”

“…The thiol, N-acetylcysteine, was selected for our studies, since it resembles a cysteine residue in a prebiotic peptide and cysteine (cystine) has been synthesized under prebiotic conditions (Sagan and Khare, 1971 ;Hong and Becker, 1979 formation of glyceraldehyde is thought to have occurred by condensation of formaldehyde (Gabel and Ponnamperuma, 1967;Reid and Orgel, 1967;Mizuno and Weiss, 1974). Formaldehyde has been produced under prebiotic conditions by a variety of reactions (Garrison et al, 1951;Miller, 1957;Getoff et al, 1960;Hubbard et al, 1971;Bar-Nun and Hartman, 1978).…”

H2S‐Mediated Thermal and Photochemical Methane Activation

“…Finally, photolysis of H 2 S molecules with 228 nm UV radiation was reported to produce “hot” reactive hydrogen radicals via Reaction (11) with a substantial translational energy capable of driving further hydrogen abstraction reactions 42. 43 In the absence of hydrogen radical scavengers, hydrogen abstraction from CH 4 can proceed, resulting in effective methane activation. The net result is that photolysis at elevated temperatures and reduced pressures should cause radical mechanisms to dominate over the S0 mechanism presented in Figure 3.…”

Nonenzymatic formation of “energy-rich” lactoyl and glyceroyl thioesters from glyceraldehyde and a thiol

“…N-acetylcysteine was used as the thiol in our reactions, since it resembles a cysteine residue 1 1 a prebiotic peptide and cysteine (cystine) has been synthesized under prebiotic conditions (Sagan and rKhare, 1971;Hong and Becker, 1979). The prebiotic synthesis of glyceraldehyde is generally considered to have occurred by oligomerization of formaldehyde (Gabel and Ponnamperuma, 1967;Reid and Orgel, 1967;Mizur.o an;.'…”