Kinetics and Mechanism of Oxidation of L-Proline by Heptavalent Manganese: A Free Radical Intervention and Decarboxylation

The kinetics of oxidation of L-proline by permanganate in alkaline medium was studied spectrophotometrically. The reaction is first order with respect to[MnO4-] and is an apparent less than unit order, each in [L-proline] and [alkali] under the experimental conditions. The reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Addition of reaction products has no effect on the reaction rate. A mechanism involving the formation of a complex between the oxidant and substrate has been proposed. The reaction constants involved in the mechanism were evaluated. There is a good agreement between the observed and calculated rate constants under varying experimental conditions. The activation parameters with respect to the slow step of the proposed reaction scheme were evaluated and discussed.

Synthesis and Characterisation of the Lithium, Sodium and Potassium Americium(β) Complexes of Hexaoxoperiodate: MI2[Am(OH)2H2IO6].xH2O

Novel complexes of trivalent Americium with hexaoxoperiodate have been prepared for the first time from an aqueous caustic solution. Chemical analysis indicated that the composition of the complexes is MI2[Am(OH)2H2IO6]. xH2O (MI= alkali metal: x = 4, MI= Na, K; X = 11, MI= Li) and all the complexes have been characterised by X-ray powder diffraction, UV-Visible, IR, and Raman spectroscopic studies, and by thermal analysis.

Kinetic and Mechanistic Study of Oxidative Degradation of Paracetamol by Diperiodatonickelate (IV) in Aqueous Alkaline Medium

A mechanism involving the monoperiodatonickelate (IV) (MPN) as the reactive species of the oxidant has been proposed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed.

Mechanistic Study of the Oxidation of Isonicotinate ion by Diperiodatocuprate(III) in Aqueous Alkaline Medium

The kinetics of oxidation of isonicotinate ion by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.60 mol dm−3 was studied spectrophotometrically. A mechanism involving the formation of an intermediate complex between the diperiodatocuprate(III) as the oxidant species and isonicotinate ion is proposed. The reaction constants involved in the different steps of mechanism have been calculated. The activation parameters with respect to the slow step of the mechanism have been computed and discussed and thermodynamic quantities were also determined.

Spectral and Mechanistic Investigations of the Oxidative Transformation of 5,5-Dimethylc Yclohexane-1,3 -Dione (Dimedone) by Quinolinium Dichromate in Perchloric Acid Medium

The kinetics of oxidation of dimedone in perchloric acid medium were studied spectrophotometrically. The reaction showed first order kinetics in quinolinium dichromate (QDC) concentration and an order of less than unity in 5,5-dimethylcyclohexane-1,3-dione [dimedone, (DM)] and acid concentrations. Increasing ionic strength had no effect on the rate, but decreasing dielectric constant of the medium decreased the rate. The oxidation reaction proceeds via a protonated chromium(VI) species, which forms a complex with dimedone. The latter decomposes in a slow step to give a free radical derived from dimedone and chromium(V), which is followed, by subsequent fast steps to give the products. The reaction constants involved in the mechanism have been evaluated. There is good agreement between the observed and calculated rate constants under different experimental conditions. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.

Oxidation of Isoniazid by Quinolinium Dichromate in an Aqueous Acid Medium and Kinetic Determination of Isoniazid in Pure and Pharmaceutical Formulations

The kinetics of oxidation of isoniazid in acidic medium was studied spectrophotometrically. The reaction between QDC and isoniazid in acid medium exhibits (4:1) stoichiometry (QDC:isoniazid). The reaction showed first order kinetics in quinolinium dichromate (QDC) concentration and an order of less than unity in isoniazid (INH) and acid concentrations. The oxidation reaction proceeds via a protonated QDC species, which forms a complex with isoniazid. The latter decomposes in a slow step to give a free radical derived from isoniazid and an intermediate chromium(V), which is followed, by subsequent fast steps to give the products. The reaction constants involved in the mechanism are evaluated. Isoniazid was analyzed by kinetic methods in pure and pharmaceutical formulations.

Kinetics and mechanistic study of the ruthenium(III) catalyzed oxidative deamination and decarboxylation of L-valine by alkaline permanganate

The kinetics of ruthenium(III) catalyzed 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 the concentration of permanganate and ruthenium(III) and less than unit-order dependence on the concentrations of L-valine and alkali. The reaction rate increases both with an increase in ionic strength and a decrease in solvent polarity of the medium. Initial addition of reaction products did not significantly affect the rate. A mechanism involving the formation of a complex between catalyst and substrate has been proposed. The activation parameters were computed with respect to the slowest step of the mechanism.Key words: oxidation, L-valine, catalysis, ruthenium(III), kinetics.