Oxidation kinetics of 4-methylanisole in methanol solution at carbon electrodes

A quantitative investigation of the electrochemical oxidation of 4-methylanisole in methanol solution at carbon electrodes has been performed. The oxidation reaction is shown to be complex, resulting in the formation not only of the corresponding diacetal, but also of several intermediate products and side products. Voltammetric measurements and preparative batch syntheses reveal a substantial influence of the choice of both electrode material and supporting electrolyte. The highest selectivity and the most rapid reaction rates are observed at graphite electrodes with potassium fluoride supporting electrolyte, whereas polished surfaces of glassy carbon are far less reactive and result in substantial formation of side products. The observed oxidation kinetics can be represented with a simple empirical model, consisting of three oxidation steps in series yielding respectively an ether, an acetal and an ester. The experimental voltammetric curves have been used to determine the anisole diffusivity in the electrolyte solution and provide fitted values for the kinetic parameters of the three oxidation steps.