• Vangalur S Srinivasan

      Articles written in Journal of Chemical Sciences

    • Micellar catalysed oxidative cyclisation of 1,3,5-triaryl formazan

      R Balakrishnan P S Raghavan Vangalur S Srinivasan

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      The kinetics of Tl(III) acetate oxidation of 1,3,5-triaryl formazan has been studied in 90% aqueous HOAc, in the presence of added anionic detergent, sodium-lauryl sulphate(NaLS) and cationic detergent, cetyltrimethylammonium bromide (ctab). Both surfactants enhance the reaction rate, indicating that the reactive species involved is possibly neutral. From the substituent influence observed in the micellar phase Hammett correlations have been attempted. Higher negative ϱ values obtained in the presence of ctab, indicate that the transition state is more electron-deficient. The positive co-operativity calculated for the micellar catalysed reactions (3.0) indicates possible hydrophobic interaction between micelle and formazan.

    • Oxidation of benzaldehyde semicarbazone by Tl(III) acetate—a structure reactivity correlation

      R Balakrishnan Vangalur S Srinivasan

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      The kinetics of Tl(III) acetate oxidation of semicarbazones of benzaldehyde and substituted benzaldehydes have been investigated in aqueous (90%) acetic acid. Electron-releasing substituents in the phenyl ring enhance the rate of the reaction, whereas electron-withdrawing substituents retard the rate. The rho value of −1 favours electron-deficient transition state. To account for the major product of the reaction,viz respective benzaldehyde, a suitable scheme involving N-thallated intermediate has been proposed

    • Electron transfer to oxochromate(V) mediated through a sulphur bond

      A Rajavelu Vangalur S Srinivasan

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      Reduction of carboxylato bound chromium(V) by several reducing agents such as N2H4, NH2OH, Ti(III), Fe(II), VO2+, U(IV) formed part of earlier studies in which electron transfer to Cr(V) seems to occur through nitrogen or by inner or outer sphere path. In the chromium(V) oxidation of lactic acid, saturation kinetics has been observed and the association constant,K, evaluated from a double reciprocal plot, indicates weak interaction between reactants. In contrast, the reduction of Cr(V) by thiolactic acid exhibits total second order kinetics-first order with respect to each reactant. Probably the Crv-S bond is weaker than the Crv-O bond and electron transfer mediated through the sulphur system is facile. Under identical conditions Cr(VI) seems to be a better oxidant for lactic than for thiolactic acid.

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