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.