Homolytic aromatic substitution. Part XXXV. The thermal decomposition of benzoyl peroxide in aromatic solvents in the presence of nitrobenzene

Abstract

A mechanistic scheme is suggested which rationalises the effect of added nitrobenzene on the nature of the products from the thermal decomposition of benzoyl peroxide in benzene. A small fraction of the nitro-compound is reduced to nitrosobenzene, which scavenges phenyl radicals to form diphenyl nitroxide. The nitroxide radicals efficiently oxidise phenylcyclohexadienyl radicals to biphenyl, and thus prevent side-reactions (e.g., dimerisation), which would give high molecular weight products. The nitroxide is regenerated by oxidation of diphenylhydroxylamine by molecular benzoyl peroxide. Evidence in support of this scheme is evaluated, and several complicating features are discussed.