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The kinetics of the oxidation of mandelic acid (MA) by permanganate in aqueous alkaline medium at a constant ionic strength of 1.0 mol dm À3 were studied spectrophotometrically. The reaction shows first-order kinetics in [permanganate ion] and fractional order dependences in [MA] and [alkali]. Addition of products, manganate and aldehyde have no significant effect on the reaction rate. An increase in ionic strength and a decrease in dielectric constant of the medium increase the rate. The oxidation process in alkaline medium under the conditions employed in the present investigation proceeds first by formation of an alkali permanganate complex, which combines with mandelic acid to form another complex. The latter decomposes slowly followed by a fast reaction between the free radical of mandelic acid and another molecule of permanganate to give products. The reaction constants involved in the mechanism were derived. There is good agreement between the observed and calculated rate constants under different experimental conditions. The reaction was studied at different temperatures and activation parameters were computed with respect to the slow step of the proposed mechanism.

The kinetics of the oxidation of 1,10-phenanthroline (1,10-phen) by permanganate were investigated in alkaline medium. A first-order, fractional-order and zero-order dependence of the rate each in [MnO 4 À ], [1,10-phen] and [OH À ], respectively, was observed. The data suggest that the oxidation proceeds via the formation of a complex between 1,10-phen and MnO 4 À which decomposes in a slow step to yield the free radical of 1,10-phen, followed by a fast step to give 2,2'-bipyridy1 3,3'-dicarboxaldehyde. The reaction constants involved in the mechanism were evaluated. There was good agreement between the observed and calculated rate constants under varying conditions of the experiments. The activation parameters were calculated with respect to the slow step of the mechanism. Copyright

À which decomposes in a slow step to yield the free radical of 1,10-phen, followed by a fast step to give 2,2'-bipyridy1 3,3'-dicarboxaldehyde. The reaction constants involved in the mechanism were evaluated. There was good agreement between the observed and calculated rate constants under varying conditions of the experiments. The activation parameters were calculated with respect to the slow step of the mechanism. Copyright

The kinetics of oxidation of dimedone (DM) by permanganate in low and high alkali concentrations at a constant ionic strength has been studied spectrophotometrically. The reaction seems to proceed by two different mechanisms. At higher concentrations of alkali the reaction exhibits first, less than unity and zero order dependence of the rate on [permanganate ion], [DM] and [alkali], respectively, while at lower concentrations of alkali, all the orders are the same except for [OH-] the order of [OH-] is less than unity. In both the cases of [OH-], the, initial addition of products does not affect the rate significantly, while an increase in ionic strength and decrease in dielectric constant enhance the rate of the reaction. Plausible mechanisms consistent with the kinetic data were proposed and constants involved in the mechanisms have been evaluated. There is good agreement between observed and calculated rate constants at varying conditions of the experiments. The activation parameters with respect to the slow step of the mechanism have been computed.