Elementry steps and the solvent effect in electrochemical reduction of acetophenone

Abstract

Acetophenone reduction follows an electrochemically ideal type of pathway with electron and proton transfer to from ketyl radicals followed by recombination of the radicals to form the pinacol in excellent yield. Although the reaction has been studied polarographically, the limitations which this approach imposes on the examination of the electrode reaction kinetics justifies further investigations by other methods. A combination of steady-state, potentiodynamic and potential step kinetic studies have been carried out and, coupled with results obtained on the adsorption of the reactant and product, lead to a fuller understanding of the electrochemical behaviour of the reaction which is more complex than hitherto supposed in polarographic types of approach. Studies of the kinetics and adsorption behaviour, including determination of the reaction orders in ketone and H⁺, in various methanol + solvent mixtures reveal an unexpected dependence of the kinetics on the solvent composition. The consistency of various explanations for the solvent effect with the observed electro-chemical-kinetic behaviour is examined.