N-phenyl-1,4-phenylenediamine and benzidine oxidation products identified using on-line electrochemistry/electrospray fourier transform mass spectrometry

Electrochemical oxidation products of N-phenyl-1,4-phenylenediamine and benzidine formed in aqueous methanol solution at pH 4 were identified on the basis of exact molecular mass using electrochemistry coupled on-line with electrospray Fourier transform mass spectrometry. The main N-phenyl-1,4-phenylenediamine oxidation product observed was N-phenyl-1,4-phenylenediimine formed by a nominal two-electron, two-proton oxidation process. A less abundant product was identified as the quinone formed by hydrolysis of this oxidized species. In the case of benzidine, the main oxidation product was identified as the cation radical formed by a nominal one-electron oxidation process. No hydrolysis product was observed.