The reduction of Mncydtaby Co(edta)2-and Co(cydta)2-is catalyzed by aqueous micellar cetyltrimethylammonium bromide (CTAB). The maximum rate enhancements are ca. 600X and 160X, respectively. The binding between Co-(cydta)-and CTAB micelles was investigated by gel filtration chromatography using a Sephadex G-25 gel. The binding constant of Co(cydta)-, defined in terms of partitioning between bulk aqueous phase and micellar pseudophase, is 325 M-1 (25 °C) and incorporates contributions from electrostatic as well as hydrophobic interactions. The kinetic data have been interpreted in terms of Berezin's theory (assuming similar binding constants for Co(cydta)-and Mn(cydta)-) and current theories about the mechanism of electron transfer processes. This reveals that the rate constant for the bimolecular reaction in the micellar pseudophase (km) is smaller than the rate constant in aqueous solution, whereas the rate constant for the interphase reaction (£m0 involving Co(edta)2on the micellar surface and Mn(cydta)-in bulk aqueous phase is higher than ku and the rate constant in aqueous solution. Various factors which affect &m and ku are discussed taking into account the micellar surface solvent properties.
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