Stoichiometry of the oxidation of arylhydrazines with ferricyanide : Quantitative measurements of absorption spectra of aryldiazenes

A novel method for generating aryldiazenes quantitatively by the oxidation of arylhydrazines with exactly two equivalents of ferricyanide has been confirmed with o-, m-, and p- tolylhydrazine and with o- and p-hydrazinobenzoic acid. The rapidity and stoichiometry of the reaction permit accurate measurements of UV and visible absorption spectra in aqueous solution. Although oxidation of acetylphenylhydrazine by ferricyanide was slower, the product was shown to be acetylphenyldiazene. Acetylphenyldiazene is partially hydrogenated during mass spectrometric analysis. The source of hydrogen was shown to be H₂O in the spectrometer. This phenomenon, previously reported only in quinones, was also observed in the mass spectrum of methyl phenyldiazenecarboxylate.