Diprotonated hydrazones and oximes as reactive intermediates in electrochemical reductions

The shape of plots of limiting currents of some hydrazones and oximes as a function of pH, the slopes of E1/2–pH plots (particularly for benzaldehyde N,N,N-trimethylhydrazonium ion) and the presence of separate two or three waves in reductions of some oximes bearing electron withdrawing groups represent a proof of formation of diprotonated forms of hydrazones and oximes as reaction intermediates. They are formed at the surface of the electrode in an equilibrium preceding the uptake of the first electron.