Reactions of Nitrosoarenes with Nitrogen Monoxide (Nitric Oxide) and Nitrogen Dioxide: Formation of Diarylnitroxides

Nitrosoarenes react with nitrogen monoxide (nitric oxide) at room temperature and in aprotic media to afford the corresponding diarylnitroxides by the intermediate formation of N ‐nitrosoarylnitroxides. However, these latter spin adducts, in contrast with literature reports, have never been detected by us. N ‐nitrosophenylnitroxide is obtained only in the oxidation of the ammonium salt of N ‐nitrosophenylhydroxylamine (cupferron) with trace amounts of lead tetraacetate. However, it evolves with time to diphenylnitroxide, as demonstrated by following the reaction course in the ESR cavity. On a macroscale level, the reaction between nitrosobenzene and nitric oxide leads to the formation of N ‐nitrosodiphenylamine, 4‐nitro‐ N ‐nitrosodiphenylamine, 4‐nitrodiphenylamine and 4,4′‐dinitrodiphenylamine, in addition to diphenylnitroxide. Diarylnitroxides are also obtained when nitrosoarenes react with small amounts of nitrogen dioxide; the mechanism of this reaction is proposed and discussed. The structure of 4‐nitro‐ N ‐nitrosodiphenylamine was determined by X‐ray analysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)