Oxidation of phenylhydroxylamine in aqueous solution: a model for study of the carcinogenic effect of primary aromatic amines

Phenylhydroxylamine is degraded in aqueous phosphate buffers at physiological pH values (6.8-7.4) to give nitrosobenzene, nitrobenzene, and azoxybenzene. The reaction is O2 dependent and subject to general acid and general base catalysis. At pH less than or equal to 5.8 in cacodylate buffer, it is converted to p-nitrosophenol in addition to nitrosobenzene, nitrobenzene, and azoxybenzene. Nitrobenzene and p-nitrosophenol appear to form directly from phenylhydroxylamine. A common intermediate generated from phenylhydroxylamine and O2 is suggested to account for the formation of nitrobenzene, nitrosobenzene, and p-nitrosophenol and is consistent with kinetic studies and 18O-labeling experiments. The results suggest that neither hydrogen peroxide nor superoxide (O-2) are involved in the oxidation sequence.