INFLUENCE OF OXIDATIVE TREATMENT OF COPPER GRID ELECTRODES ON THE EFFICIENCY OF CONVERSION TO ANILINE IN THE ELECTROREDUCTION OF NITROBENZENE AND AZOBENZENE IN BASIC AQUEOUS-METHANOL

The influence of preoxidizing the surface of polycrystalline copper el ectrodes on the efficiency of the controlled potential electrochemical reduction of nitrobenzene and azobenzene to aniline in basic aqueous methanol has been investigated. Electrodes electrochemically preoxidiz ed to Cu(OH)(2) or to Cu2O gave high yields of aniline (90-100%) with high current efficiencies (88-99%) for the electrohydrogenation of nit robenzene compared to electrodes preoxidized by air (7-29% of aniline, 64-74% current efficiency). For the electrohydrogenation of azobenzen e, copper electrodes preoxidized to Cu2O were found to be more active (average yield of aniline of 28%, average current efficiency of 55%) t han electrodes preoxidized to Cu(OH)(2) (3-11% of aniline, 42-53% curr ent efficiency), and electrodes preoxidized by air were inactive (the electrohydrogenation stopped at hydrazobenzene). The improvement of ac tivity induced by preoxidation of the copper surface is linked to the increase of the surface area.