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The kinetics and mechanism of uncatalyzed and ruthenium(III) catalyzed oxidation of vanillin (Van) by periodate were studied in alkaline medium at 298 K, and at constant ionic strength of 0.3 molÁdm -3 . The reaction exhibits 1:1 stoichiometry ([Van]:[periodate]). The reaction shows first-order kinetics in [periodate] and [Ru(III)] and less than unit order with respect to [Van] and [OH -]. The ionic strength and dielectric constant of the medium did not affect the rate significantly. The main products were identified by spot tests, melting temperature and FT-IR. From the effect of temperature on the reaction rate, the Arrhenius and activation parameters have been calculated. The catalytic constant (K C ) was also calculated for Ru(III) catalysis at different temperatures. Plausible mechanisms have been proposed and rate laws explaining the experimental results are derived. Kinetic studies suggest that the active species of periodate and Ru(III) were [H 2 IO 6 ] 3-and [Ru(H 2 O) 5 OH] 2? , respectively. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism, along with the corresponding thermodynamic quantities, were determined and discussed.

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The oxidation of a Vitamin B 6 by diperiodatoargentate (III) (DPA) was carried out in presence of ruthenium (III) catalyst in the alkaline medium at 25 • C and at a constant ionic strength of 0.50 mol dm −3 spectrophotometrically. The reaction was first order with respect to [DPA] whereas the apparent order with respect to Vitamin B 6 , Ru (III) and alkali concentrations were less than unity. The order changes from first order to zero order as the Vitamin B 6 and alkali concentrations were increased. Addition of periodate had no effect on the rate of the reaction. Effect of added products, ionic strength and dielectric constant of the reaction medium has been investigated in the presence of Ru (III). The reaction in an alkaline medium proceeds via Ru(III)-Vitamin B 6 complex, which further reacts with one mole of DPA in the rate determining step to give the product. The reaction constants involved in the different steps of the mechanism were calculated. The catalytic constant (K C ) was also calculated at different temperatures. The activation parameters with respect to the slow step of the mechanism were determined and discussed.