A CASE OF THE INDIRECT ROLE OF TRACES OF WATER IN THE ELECTROREDUCTION OF ORGANIC SUBSTRATES

Adventitious water is often the main protonating agent towards the bas ic intermediates of organic electrode reductions in dipolar non-protog enic solvents. OH- ions thus formed do not generally modify the reduct ion pattern, unless they are able to catalyze the transformation of so me of the species involved in the electrode process. This is the case in the two-electron reduction of Ph(3)CSC(6)H(4)CN in DMF, which invol ves proton transfer from residual water to the reduction intermediate Ph(3)C(-). The ensuing OH- ions catalyze hydrolysis of the substrate, with formation of the corresponding amide. The hydrolysis process is s ufficiently fast to show its effect not only during macroscale electro lysis but also in the much shorter time scale of low sweep rate cyclic voltammetry. However, the reaction can easily be hampered by addition of even mild proton donors, thus causing only minor perturbations in the reaction medium.