• Vinita Sharma

      Articles written in Journal of Chemical Sciences

    • Kinetic study of the oxidation of aliphatic aldehydes bybis(2,2′-bipyridyl) copper(II) permanganate

      Seema Kothari Vinita Sharma Pradeep K Sharma Kalyan K Banerji

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      Kinetics of oxidation of aliphatic aldehydes, to the corresponding carboxylic acids, by bis(2,2′-bipyridyl)copper(II) permanganate (BBCP) has been studied. The reaction is first order with respect toBBCP. Michaelis-Menten type kinetics were observed with respect to the aldehyde. The formation constants for the aldehyde-BBCP complexes and the rates of their decomposition, at different temperatures, have been evaluated. Thermodynamic parameters for the complex formation and the activation parameters for their decomposition have also been determined. The reaction is catalysed by hydrogen ions; the acid-dependence being of the form:kobs = a +b [H+]. The oxidation of MeCDO exhibited a substantial kinetic isotope effect (kH/kD = 4.33 at 303 K). The role of aldehyde hydrate in the oxidation process has been discussed. A mechanism involving formation of permanganate ester and its slow decomposition has been proposed.

    • Kinetics and mechanism of the oxidation of diols by bromine in acid solution

      Vinita Sharma Pradeep K Sharma Kalyan K Banerji

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      Kinetics of oxidation of five vicinal diols, four non-vicinal diols, and two of their monoethers by bromine in strong acid solutions have been studied. The vicinal diols yielded the products arising out of glycol bond fission while the other diols yielded the hydroxycarbonyl compounds. The reaction is first order with respect to both bromine and the diol. The rate decreases with an increase in the acidity. The oxidation of [1,1,2,2-2H4] ethanediol showed the absence of a primary kinetic isotope effect. The value of solvent isotope effect, k(H2O)/k(D2O), at 303 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutane-1-ol are 4.71, 1.04 and 1.07 respectively. A mechanism involving a glycol bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism as are monohydric alcohols.

    • Kinetics and mechanism of oxidation of aliphatic primary alcohols by quinolinium bromochromate

      Sonu Saraswat Vinita Sharma K K Banerji

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      Oxidation of nine aliphatic primary alcohols by quinolinium bromochromate (QBC) in dimethylsulphoxide leads to the formation of the corresponding aldehydes. The reaction is first order with respect to both QBC and the alcohol. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form:kobs = a + b[H+]. The oxidation of [1,1-2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect. The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft’s and Swain’s multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.

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