The Mechanism of Decomposition of Azo Compounds. I. 1,1'-Azocyanocyclohexane and N-(1-Cyanocyclohexyl)-pentamethyleneketenimine

Abstract

The rates of formation of N-(1-cyanocyclohexyl)-pentamethyleneketenimine (RR') from 1,1'-azocyanocyclohexane (RN_2 R) have been followed at 80 and 100° with and without the presence of radical scavengers. The initial rate of formation of RR' is significantly decreased in the presence of scavengers. This provides evidence for the coexistence of two paths for the formation of RR'. We believe that one is by primary recombination of pairs of cyanocyclohexyl radicals (R•) in the solvent cage and that the other is by coupling of radicals which have been separated from their original partners by diffusion. The ketenimine has been isolated in pure form, and its rates of decomposition under various conditions have been found to follow first-order kinetics. The rate of decomposition of RR' is significantly accelerated in the presence of scavengers. This is consistent with a radical mechanism; the "free" R• which are scavenged are thereby prevented from coupling to regenerate RR'. The rates of decomposition of RN_2R at 80 and 100°, the efficiencies of radical production from both RN2R and RR', and the rates of cumene oxidation initiated by RN_2R and RR' have also been studied. These data make possible a complete analysis of the distribution of radicals formed in the decomposition of RN_2R.

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