ENHANCED RATES OF ORGANIC DEHALOGENATIONS IN A MICROEMULSION USING ADSORBED METAL PHTHALOCYANINES ON ELECTRODES

Copper and nickel phthalocyanines and their tetrasulfonates adsorbed o nto carbon electrodes were used for electrochemical catalytic reductio n of 1,2-dibromobutane (DBB), trans-1,2-dibromocyclohexane (DBCH), and trichloroacetic acid (TCA) in a bicontinuous microemulsion made from didodecyldimethylammonium bromide (DDAB), dodecane, and water and in h omogeneous acetonitrile/water. Square wave voltammetry was used to obt ain apparent pseudo-first-order rate constants (k') for the rate-deter mining step (rds) involving reaction of organohalides with catalysts r educed by two electrons. Reductions of DBCH and DBB gave larger k' val ues in the microemulsion than in homogeneous solvent. For reduction of TCA, larger k' values were found in the homogeneous solvent. Results suggest that DBCH and DBB give higher reaction rates in the microemuls ion because of preconcentration of the relatively nonpolar organohalid es into a surfactant film on the MPCTS-coated electrode. TCA may be pa rtly rejected from the film, decreasing its reaction rate. Thus, when using electrodes with adsorbed catalysts in microemulsions, reactant c oncentration in an adsorbed film on the electrode appears to be an imp ortant rate-controlling factor.