On the mechanism of the gamma-radiolysis of deoxygenated aqueous solutionsof hydrazine

A reaction mechanism has been devised by trial and error that accounts for most of the data that have been obtained from gamma -radiolysis studies und er deaerated conditions and which hitherto have not been satisfactorily exp lained. The major features of the proposed mechanism are the following. (a) Hydrazyl radicals N2H4.+ and (N2H3)-N-. react by disproportionation to for m N2H2 and hydrazine, and by combination either as the free radicals or wit h one of them complexed with a hydrazine molecule, N2H5+ or N2H4, to produc e N-2+2NH(3). This accounts for the observed strong dependence of the radio lytic decomposition yields (G-values) on [N2H5+]. (b) Hydrogen atoms (hydra ted electrons) are proposed to react with N2H5+ (N2H4) by a split path to f orm H-2+N2H4.+ ((N2H3)-N-.) and (NH2)-N-.+NH4+ (NH3), which helps to accoun t for the observed values of G(H-2); reduction of N2H2 by H-. to (N2H3)-N-. is also required to explain fully the values of G(H-2). (c) In alkaline so lution the decrease in decomposition yields is explained in terms of the di ssociation of H2O2 to HO2-, which is more readily oxidised to O-2(.-). This , together with the much longer lifetime of O-2(.-) at high pH, results in the reduction by O-2(.-) of (N2H3)-N-. back to N2H4. The effect of added H2 O2 in acidic solution can be explained if it forms a complex with N2H4.+ fo llowed by reaction with another N2H4.+ to form N-2+2H(2)O.