On the pH-dependence of polarographic half-wave potentials II. Protonation of an electro-inactive group

Abstract

The pH-dependence of half-wave potentials of reversible and irreversible electrode reactions has been studied for a depolarizer bearing, besides the electroactive, an electroinactive acidic/basic group. Solution of two theoretical cases of an irreversible two-electron reduction indicates that the break which may occur on the E 1/2 vs . pH plot does not denote the dissociation constant p K A of the acidic form of the electroinactive group. The qualitative conclusions from the solution have been discussed for some examples of the reduction of nitrobenzene derivatives.