The electrochemical oxidation of VB was examined in both acetonitrile and propylene carbonate. In both solvents, the depolarizer behaved similarly, except for differences arising from the high viscosity of PC and its attack by the added acid or base when the time of the experiment was longer than half an hour. An oxidation mechanism is proposed which comprises a primary one-electron transfer followed by deprotonation, then another electron transfer accounting for an e.c.e. sequence. In neutral solution one VB molecule is oxidized to N-[4-methoxyphenyl] quinonediimine in the first wave (peak) giving its proton to another neutral depolarizer molecule. The latter undergoes oxidation at the potential of the second wave (peak). This view is supported by the observed effect of the addition of HClO4(acid) and diphenylguanidine (base) on the polarograms, in which the oxidation potential is greatly affected by the proton availability in solution. © 1972 Elsevier Sequoia S.A., Lausanne.
Farsang, G., Kovács, M., Saber, T. M. H., & Ladányi, L. (1972). The study of the electrochemical oxidation mechanism of diphenylamine derivatives in dipolar aprotic solvents. 1. The electrochemical oxidation of variamine blue in acetonitrile and in propylene carbonate. Journal of Electroanalytical Chemistry, 38(1), 127–135. https://doi.org/10.1016/S0022-0728(72)80098-6