The photolysis of acyclic azines and the electronic spectra of R1R2CN • radicals

TLDR: In this paper, the absolute rate constant for the second-order decay of the CH 2 N • radical has been determined and the pressure dependence of the product quantum yields from the continuous 253.7 nm photolysis of acetaldazine was investigated.

Abstract: Flash photolysis of formaldazine, acetaldazine and dimethylketazine produced three new transient u.v. spectra which have been attributed to the CH 2 N., CH 3 CHN. and (CH 3 ) 2 CN. free radicals. The absolute rate constant for the second-order decay of the CH 2 N • radical has been determined. The pressure dependence of the product quantum yields from the continuous 253.7 nm photolysis of acetaldazine was investigated. The results from these experiments, and a re-interpretation of the data published by Brinton on acetaldazine photolysis, have been used to derive a free radical mechanism which includes several primary reactions, of which NN fission is the major process under all experimental conditions, and a sequence of secondary reactions in which the disproportionation of CH 3 CHN. radicals predominates. The overall mechanism satisfactorily describes the pressure and wavelength dependence of acetaldazine photolysis. Preliminary experiments on formaldazine indicate that the photolysis of the azine proceeds by a very similar mechanism.