Liquid–liquid interface electrochemistry applied to study of a two-phase permanganate oxidation

Abstract

Using as an example the oxidation of cis-cyclooctene in dichloroethane by aqueous permanganate, we show how to apply electrochemical methods to gain understanding of a two-phase oxidation reaction. This reaction is found to be too slow for the timescale of conventional cyclic voltammetry so an analogue of stripping voltammetry (cyclic stripping chronoamperometry) is here applied to analyse the kinetics of the homogeneous reaction in the organic phase. Permanganate is transferred from water to DCE with a rapid potential scan, held for an appropriate time, then stripped out, back into the aqueous phase by a potential scan. The experimental data of stripping peak current against holding time and reagent concentration are compared to a simulation model involving an irreversible second-order reaction of permanganate with the cyclic alkene in the organic phase, following an electrochemically reversible transfer across the liquid/liquid interface, in order to derive the rate constant for formation of the manganate ester, which is the first step of the reaction: k≈1.5 mol −1 dm 3 s −1 .