MICELLAR ACCELERATED REDUCTION OF ETHYLENEDIAMINETETRAACETATO-COBALTATE(III) BY 1-BENZYL-1,4-DIHYDRONICOTINAMIDE

The electrostatic and hydrophobic effects of ionic micelles on the reduction of ethylenediaminetetraacetato cobaltate(III) ([Co(edta)]-) by 1-benzyl-1,4-dihydronicotinamide (BNAH) were investigated with dodecyltrimethylammonium chloride (DTAC) and/or sodium dodecyl sulfate (SDS). Cationic DTAC accelerated the reduction of [Co(edta)]-, while anionic SDS retarded the reaction. The micellar effects of DTAC on the present reaction at 30-degrees-C were kinetically analyzed by using the ion-exchange model and the Berezin's approach: the evaluated rate constant, (1.0 +/- 0.1-1.1 +/- 0.4)x 10(-4) mol-1 dm3 s-1, for the micellar-phase reaction was ten times smaller than that, 1.46 x 10(-3) mol-1 dm3 s-1, for the aqueous-phase one. This fact was well-explained by the electron-transfer rate constant calculated with the experimentally determined redox potentials of BNAH and [Co(edta)]-. The cationic DTAC micelles, however, resulted in considerably larger value (3.58 x 10(-3) mol-1 dm3 s-1) of overall reaction rate constant than that (1.46x10(-3) mol-1 dm3 s-1) of nonmicellar one, because the apparent concentrations of the reactants in the micellar phase increased remarkably by condensation of BNAH and [Co(edta)]- to the micelles through the hydrophobic interaction and the electrostatic interaction, respectively.