Electrochemical catalysis in microemulsions. Dynamics and organic synthesis

Microemulsions are clear microheterogeneous fluids made from water, oil, and surfactant. They provide cheaper and less toxic alternatives to organic solvents. In this paper, we review progress in understanding reaction dynamics and designing mediated electrochemical syntheses in microemulsions. Rates of mediated electrochemical reactions in conductive microemulsions can be enhanced by preconcentration of reactants in a dynamic film on the electrode surface, or more generally by controlling the formal potential of the mediator in the fluid. The electrode/fluid interface in microemulsions probably consists of a dynamic layer of surfactant molecules packed more loosely on the electrode than in aqueous micellar solutions. Microemulsions afforded good yields of carbon-carbon addition products in reactions mediated by the cobalt complex vitamin B-12. Excellent stereoselective control in microemulsions made with the cationic surfactant cetyltrimethylammonium bromide was demonstrated for the catalytic cyclization of 2-(4-bromobutyl)-2-cyclohexen-1-one to 1-decalone. Electrochemical synthesis in microemulsions may be a viable future approach to environmentally friendly methods of producing organic chemicals. (C) 1997 Elsevier Science S.A.