EPR and polarography of nitroazoles. 5. First step in the electrochemical reduction of 2-substituted 5(6)-nitrobenzimidazole using a rotating platinum ring-disk electrode

Abstract

Using a rotating platinum ring-disk electrode, the electrochemical reduction of 2-substituted 5(6)-nitrobenzimidazoles at the platinum disk in acetonitrile and the oxidation of their radical anions at the ring were studied. During the reduction molecular hydrogen forms by a bimolecular reaction of two primary radical anions. The correlating of electrochemical quantities with the σI, σR, and σ substituent constants are evidence that E 1 2/d depends on substituent resonance and induction effects to about the same extent, whereas i lim d , n, and E 1 2/r depend predominantly on the resonance effect.