LIQUID LIQUID INTERFACE AS A MODEL SYSTEM FOR STUDYING ELECTROCHEMICAL CATALYSIS IN MICROEMULSIONS - REDUCTION OF TRANS-1,2-DIBROMOCYCLOHEXANE WITH VITAMIN-B-12/

A complex electrochemical catalytic reaction was investigated at the i nterface between water and benzonitrile as a model for interfacial che mistry in microemulsions. Structures similar to those between oil-wate r microphases in microemulsions were created by using the interface be tween two immiscible electrolyte solutions (ITIES). While interfacial area in a microemulsion can be uncertain, the ITIES is well-defined an d can be used to evaluate relevant heterogeneous inter-facial kinetics . The reaction between the Co(I) form of vitamin B-12 generated electr ochemically in the water phase, and trans-1,2-dibromocyclohexane (DBCH ) in benzonitrile was probed directly at the ITIES by scanning electro chemical microscopy (SECM). Apparent heterogeneous rate constants for the interfacial reaction were extracted from SECM current-distance cur ves, Influences of reactant concentration, potential drop across the I TIES, and adsorbed surfactants were investigated. Results suggest that the kinetics of reduction of DBCH by B-12 Co(I) are more complex at a liquid/liquid interface than that of the simple second-order rate-lim iting process in a homogeneous organic solvent.