A systematic search for aldehydes, ketones, and carboxylic acids was carried out in aqueous solutions of HCN, <tex-math>${\rm NH}_{4}{\rm CN},\ {\rm CH}_{3}{\rm CN}$</tex-math>, and <tex-math>${\rm C}_{2}{\rm H}_{4}{\rm CN}$</tex-math>, that had received multikilogray doses of 60 Co γ radiation. About 30 radiolytic products were identified, among them a large variety of dicarboxylic and tricarboxylic acids. Some of them might be of significant interest in molecular evolution studies of prebiotic processes. They originate in the free-radical-initiated chemical reactions where the additional oligomerization processes are particularly important. Most of the radiolytic products appear in both cyanides and nitriles and point to the importance of reactions involving the carbon-nitrogen triple bond.

Oxygen-free aqueous solutions of 0.1 M ${\rm NH}_{2}{\rm CN}$ (pH 2.4 and 5) were irradiated with γ rays (0.01-25 Mrad). The rate constants determined in competition experiments are: $k({\rm H}+{\rm NH}_{2}{\rm CN})=6.7\times 10^{6}\ M^{-1}\ {\rm sec}^{-1},k(e_{{\rm aq}}{}^{-}+{\rm NH}_{2}{\rm CN})=1.5\times 10^{9}\ M^{-1}\ {\rm sec}^{-1}$ , and $k({\rm OH}+{\rm NH}_{2}{\rm CN})=8.5\times 10^{6}\ M^{-1}\ {\rm sec}^{-1}$ . Radiation-chemical yields were determined for the decomposition of cyanamide molecules and the formation of several radiolytic products. The following compounds were identified in irradiated solutions: ${\rm H}_{2},{\rm CO}_{2},{\rm NH}_{3}$ , urea, biuret, arginine, and a -N=N- molecule assigned to methylaminoazoformamide. Possible reactions of secondary free radicals leading to the formation of radiolytic products were considered by taking into account the model of water radiolysis and the measured radiation yields.

Oxygen-free aqueous solutions of 0.1 M ammonium and sodium cyanides were exposed to large doses of 60 Co γ rays. Radiation-chemical yields were determined for the decomposition of cyanide molecules, as were the total amount of nitrogen in nonvolatile nitrogen-containing radiolytic products, the free ammonia, and the yields of several amino acids released on acid hydrolysis of irradiated samples. Positive biuret reaction was found and its intensity used for an estimation of amide bond yields. Up to 18% of the nitrogen from nonvolatile radiolytic products appears in the amide bond, and up to 14% appears in natural amino acids. The origin of peptidic material is attributed to the polymerization initiated by cyano radicals produced in reactions of cyanides with OH, H, and <tex-math>$e{}_{{\rm aq}}{}^{-}$</tex-math> species from radiolyzed water.

The radiolytic behavior of HCN was studied in dilute (0.1 M) oxygen-free solutions at their natural pH and at pH 2.4. The solutions were exposed to high doses of 60 Co gamma rays (up to 16 Mrad) causing large decompositions (up to 90%). The decomposition yield, G(-HCN), and the radiation-chemical yields of formation of NH 3 , HCHO, H 2 , CO 2 , and of seven amino acids were determined. Also, the total yields of nitrogen in nitrogen-containing nonvolatile compounds, G(N), were measured. The irradiated solutions exhibited positive biuret reaction and the absorbancies depend on both the dose and the initial pH. Histidine, aspartic acid, threonine, serine, glutamic acid, alanine, and glycine were found in irradiated samples. Glycine was found to be the most abundant among the radiolytically produced amino acids; strong acid hydrolysis increases its yield by one or two orders of magnitude in samples irradiated initially at pH 2.4 as well as at their natural pH. The release of amino acids on hydrolysis and the positive biuret reaction suggest the presence of peptidic material in irradiated samples both at acid and neutral pH's. To account for these findings the formation of polymers (or their segments) having a peptidic structure was taken into consideration. The polymerization reactions were assumed to be initiated by the free radicals which were produced by HCN reactions with H, OH, and <tex-math>$e_{{\rm aq}}{}^{-}$</tex-math> species. It has been concluded that the radiolysis of dilute aqueous solutions of HCN offers significant information on the eventual role of ionizing radiation in prebiotic chemical evolution in aqueous media.

A study has been made of the radiolytic behavior of dilute, neutral, oxygen-free aqueous solutions of CH 3 CN and <tex-math>${\rm C}_{2}{\rm H}_{5}{\rm CN}$</tex-math>. Small-molecular products were identified as RCHO, NH 3 , CO 2 and H 2 . The decomposition of nitrile is followed by high yields of formation of the nonvolatile nitrogen-containing compounds, G(N). The irradiated solutions exhibit a positive biuret reaction. Several amino acids were identified among radiolytic products, and glycine and alanine were found to be the most abundant for CH 3 CN and <tex-math>${\rm C}_{2}{\rm H}_{5}{\rm CN}$</tex-math>, respectively. Their yields increased after strong acid hydrolysis of the irradiated samples. The free radicals formed by reactions of RCN with H, OH, and <tex-math>$e_{{\rm aq}}{}^{-}$</tex-math> were found to be important for the phenomena observed. It has been suggested that the positive biuret reaction, ir spectra, and the release of amino acids on acid hydrolysis provide some evidence on the formation of peptidic materials and might be of interest for the evaluation of the role that ionizing radiation might have played in prebiotic chemical evolution in aqueous media.