Radiolysis of Hydrogen Cyanide in an Aqueous System. II. Effects of Additives and Reaction Mechanism

The 60Co γ-irradiation of dilute aqueous solutions of hydrogen cyanide (6 mM) in the absence of oxygen yielded mainly ammonia with G=1.9, formaldehyde with G=1.1, and carbon dioxide with G=0.8, while G(–HCN)=5.8 molecules per 100 eV. Polymeric hydrogen cyanide was also observed with the G(–HCN(polymer))\simeq4, which showed an intense broad absorption band in the UV region upon γ-irradiation. The following material balances were observed with the main products:G(-HCN)\simeqG(NH_3)+G(-HCN(polymer))\simeqG(CO_2)+G(HCHO)+G(-HCN(polymer)) The results can be interpreted in terms of a mechanism involving HCN−, H2CN, and H(OH)CN radicals. The ratio of the rate constants for the reactions of e−aq and H atoms with hydrogen cyanide to those with several scavengers have been determined as k(e−aq + HCN)/k(e−aq + NO3−)=0.019 and k(H + HCN)/k(H + 2-propanol)=1.4, all at 17°C.

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