ELECTROCHEMICAL REDUCTION OF BROMONITRILES - MECHANISM AND POLAROGRAPHIC MAXIMA

The electrochemical reduction of ?-, ?-,?- and ?-bromonitriles (BrCR'2(CH2)nCN: R' = CH3 n = 0 (I); R' = H, n = 1 (II); R' = H, n = 2 (III); R' = CH3, n = 3 (IV)) was studied at Hg and glassy carbon electrodes in dimethylformamide solutions containing Et4NClO4 as the supporting electrolyte. Analyses performed on the solutions after controlled-potential electrolyses indicated that the nature and yield of the reduction products depend on the electrode material and (for compound I only) also on the applied potential. In fact, the reduction of bromonitriles II-IV always involves the uptake of two electrons per molecule, while, for compound I, one or two electrons are consumed according to the potential and nature of the electrode. A satisfactory description and interpretation of the polarographic maxima were achieved by means of techniques such as ac, dc and NP polarography, and cyclic voltammetry. These maxima are of the first kind and can be related to the interaction of the one-electron reduction intermediates with the mercury