The Self Oxidation Reduction of N-Arylhydroxylamines

The reactions of N-phenylhydroxylamine in the presence of dry hydrogen chloride to form azoxybenzene, aniline, 2-chloroaniline and 4-chloroaniline were studied. The molar ratio of the azoxybenzene and aniline obtained was very close to one. A similar reaction was also observed for 2-methyl- and 4-methyl-N-phenylhydroxylamine. A reasonable explanation is that N-phenylhydroxylamine undergoes a self oxidation reduction reaction to give aniline and nitrosobenzene, and the latter subsequently reacts with N-phenylhydroxylamine to give azoxybenzene. The reaction of N-phenylhydroxylamine, catalyzed by trifluoroacetic acid to yield azoxybenzene, was previously studied by Okamoto et al. and was suspected to undergo a similar reaction. We repeated the reaction and evidence for the same self oxidation reduction reaction was found. A mechanism involving the anilenium ion is proposed to account for this reaction.