Cyclic voltammetry at microdroplet modified electrodes.: A comparison of the reaction of vicinal dibromides with vitamin B12s at the liquid/liquid interface with the corresponding homogeneous process:: evidence for polar-solvent effects at the liquid/liquid interface

The electrocatalytic reactions of vitamin B-12s with three vicinal dibromides (cis-1,2-dibromocyclohexane, trans-1,2-dibromocyclohexane and 1,2-dibromobutane) are investigated in homogeneous and heterogeneous media. In the latter, cyclic voltammetry with basal plane pyrolytic graphite electrodes modified with microdroplets of dodecane + dibromide is employed to obtain kinetic parameters for the liquid/liquid reaction. The homogeneous and interfacial reactions exhibit marked differences in reactivity and the contrasting behaviour of the two systems suggests the liquid/liquid interface has a major role in the B-12s/R-Br2 reaction, consistent with a polar solvent effect. (C) 2004 Elsevier B.V. All rights reserved.