Para-phenylenediamine oxidation at a platinum electrode in acetonitrile solutions

Abstract

p-Phenylenediamine oxidation at platinum electrodes in acetonitrile solutions has been studied under a very wide range of experimental conditions. Chronopotentiometry, rotating disc electrode and cyclic voltammetry were used as electrochemical techniques. Coulometry at constant potential and product analysis were also performed. The electrochemical reaction appears as a fast and reversible one electron exchange per molecule of PPD. The electrode reaction is further complicated by follow-up chemical reactions giving unknown products in the bulk of the solution. The whole polarization curve under steady state conditions shows two waves, while under non-steady state conditions a small wave at intermediate potentials is also apparent. The reaction pathway for the first wave was interpreted as a non-conventional e.c.e. mechanism where the parent molecule acts as a base in the chemical step. These assumptions were confirmed through experiments performed with pyridine or water addition.