Dinesh C. Bilehal

Deamination and decarboxylation in the chromium(III)-catalysed oxidation of L-valine by alkaline permanganate and analysis of chromium(III) in microscopic amounts by a kinetic method

The kinetics of CrIII-catalysed oxidation of L-valine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate and L-valine in alkaline medium exhibits 2:1 stoichiometry (KMnO4:l-valine). The reaction shows first order dependence on [permanganate] and [chromium(III)], and less than unit order dependence each in [L-valine] and alkali concentrations under the experimental conditions. However the order in [L-valine] and [alkali] changes from first order to zero order as the concentrations change from lower to higher respectively. The results suggest the formation of a complex between L-valine and the hydroxylated species of CrIII. The complex reacts further with 1 mol of alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with 1 mol of alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the mechanism were obtained and discussed. The title reaction has been utilised to analyse chromium(III) in the 26.0 ng cm−3–1.0 μg cm−3 range.

Kinetics and Mechanism of Oxidation of Bromate by Diperiodatonickelate(IV) in Aqueous Alkaline Medium--A Simple Method for Formation of Perbromate

The kinetics of oxidation of bromate by diperiodatonickelate(IV) (DPN) in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between DPN and bromate in alkaline medium exhibits 1:1 stoichiometry (DPN:bromate). The reaction shows first order dependence on [DPN] and zero order dependence in [bromate] and less than unit order dependence in alkali concentrations. Periodate has a retarding effect on the rate of reaction. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the monoperiodatonickelate(IV) (MPN) as the reactive species of the oxidant has been proposed. The reaction constants involved in the mechanism are evaluated. The activation parameters were computed with respect to the slow step of the mechanism.

Kinetic and Mechanistic Study of Oxidation of Sulfamethoxazole by Alkaline Permanganate

The kinetics of the oxidation of sulfamethoxazole (SMZ) by permanganate in aqueous alkaline medium at constant ionic strength of 0.41 mol dm m 3 was studied spectrophotometrically. The reaction is of first order in [permanganate ion] and has apparent less than unit order in both [SMZ] and [alkali]. Addition of products have no significant effect on the reaction rate. However, increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation in alkaline medium has been shown to proceed via an alkali-permanganate species, which forms a complex with SMZ. The latter decomposes slowly, followed by a fast reaction between a free radical of SMZ and another molecule of permanganate to give the products. The reaction constants involved in the mechanism were evaluated and there is a good agreement between observed rate constants and the calculated rate constants. The activation parameters were computed with respect to the slow step of the proposed mechanism.

Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of Dimethyl Sulfoxide by N-Chlorosuccinimde in Aqueous Alkaline Medium

The ruthenium(III) catalyzed oxidation of dimethyl sulfoxide by N-chlorosuccinimide (NCS) in aqueous alkaline medium is found to occur via substrate-catalyst complex formation followed by the interaction of active species of NCS viz., HOCl and the complex in a slow step to yield the products with regeneration of the catalyst. One of the products, succinimide, retards the rate of reaction. The reaction is first order in [NCS] and [Ru(III)], lower than first order in [DMSO] and of inverse fractional order in [OH-]. A suitable mechanism is proposed and the reaction constants of individual steps involved in the mechanism have been evaluated.