• Kalyan K Banerji

      Articles written in Journal of Chemical Sciences

    • Kinetics and mechanism of the oxidation of some hydroxyacids by pyridinium fluorochromate

      Rachna Asopa Saraswati Agarwal Kalyan K Banerji

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      Oxidation of glycolic, lactic and mandelic acids by pyridinium fluorochromate (PFC) leads to the formation of the corresponding oxoacids. The reaction is first order with respect to PFC. Michaelis-Menten type kinetics were observed with respect to the hydroxy acid. The values of the formation constants of the hydroxy acid-PFC complexes and the rates of their decomposition, at different temperatures, have been evaluated. Thermodynamic parameters of the complex formation and activation parameters for the decomposition of the complexes have been calculated. The oxidation of mandelic acid has been studied in 19 different organic solvents. Analysis of the solvent effect indicates that the cation-solvating power of the solvents plays the major role in reaction rate. Oxidation of α-deuteriomandelic acid indicates the presence of a primary kinetic isotope effect. The analysis of the dependence of kinetic isotope effect on temperature indicates that the reaction involves a symmetrical cyclic transition state. A suitable mechanism has been proposed.

    • Kinetics and mechanism of the oxidation of diols by pyridinium hydrobromide perbromide

      Dipti Mathur Pradeep K Sharma Kalyan K Banerji

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      Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of thier monoethers by pyridinium hydrobromide perbromide (PHPB) have been studied. The vicinal diols yield products arising out of the glycol bond fission while the other diols yield hydroxycarbonyl compounds. The reaction is first order with respect to PHPB. Michaelis-Menten type kinetics are observed with respect to the diol. There is no effect of added pyridinium bromide on the reaction. The oxidation of [1,1,2,2-2H4]ethanediol shows the absence of a primary kinetic isotope effect. The values of solvent isotope effect,k(H2O)/k(D2O), at 313K, for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 4·71, 2·17 and 2·23 respectively. A mechanism involving glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism as they are monohydric alcohols.

    • Kinetics and mechanism of the oxidation of primary aliphatic alcohols by pyridinium bromochromate

      P Aparna Seema Kothari Kalyan K Banerji

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      Oxidation of nine primary aliphatic alcohols by pyridinium bromochromate (PBC) leads to the formation of corresponding aldehydes. The reaction is of overall second order, and of first order with respect to the each reactant. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the formkobs=c+d[H+]. The oxidation of [1, 1-2H2] ethanol (MeCD2OH) exhibited a substantial primary kinetic isotope effect. The reaction was studied in nineteen organic solvents and the effect of solvent was analysed using Taft's and Swein's multiparametric equations. The oxidation is susceptible to both the polar and steric effects of the substituents. A suitable mechanism has been proposed.

    • Kinetics and mechanism of the oxidation of formic acid bybis-(2,2′-bipyridyl) copper(II) permanganate

      Baljeet Kaur Satsangi Seema Kothari Kalyan K Banerji

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      The oxidation of formic acid bybis-(2,2′-bipyridyl)copper(II) permanganate (BBCP) is first order with respect to BBCP. The order with respect to formic acid is less than one in the absence of perchloric acid whereas in the presence of perchloric acid, it is more than one but less than two. Thus in both the cases Michaelis-Menten type kinetics were observed with respect to formic acid. The overall formation constants for the formic acid-BBCP complexes and their rates of decomposition have been evaluated. Thermodynamic parameters for complex formation and the activation parameters for their decomposition have also been calculated. The hydrogen-ion dependence has the formkobs=a+b[H+]+c[H+]2. The oxidation of deuterioformic acid showed the presence of a primary kinetic isotope effect (kH/kD≈4). An increase in the amount of acetic acid in the solvent mixture, acetic acid and water, increases the rate. The addition of 2,2′-bipyridine and acrylonitrile has no effect on the rate. Suitable mechanisms have been proposed.

    • Kinetics and mechanism of oxidation of diols bybis(2,2′-bipyridyl) copper(II) permanganate

      Kavita Mohnot Pradeep K Sharma Kalyan K Banerji

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      Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of their monoethers bybis(2,2′-bipyridyl) copper(II) permanganate (BBCP), has been studied. The vicinal diols yielded the products arising out of the glycol bond fission, while the other diols yielded the hydroxycarbonyl compounds. The reaction is first-order with respect to BBCP. Michaelis-Menten type kinetics were observed with respect to the diol. There is no effect of added 2,2′-bipyridine on the reaction. The oxidation of [1,1,2,2-2H4] ethanediol showed the absence of a primary kinetic isotope effect. 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 the oxidation of phosphinic, phenylphosphinic and phosphorous acids by benzyltrimethylammonium dichloroiodate

      Deepa Suri Seema Kothari Kalyan K Banerji

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      Oxidation of lower phosphorus oxyacids by benzyltrimethylammonium dichloroiodate (BTACI), in the presence of zinc chloride, resulted in the formation of the corresponding oxyacids with phosphorus in a higher oxidation state. The reaction is first order with respect to the concentration of BTACI, oxyacid and zinc chloride. The reaction exhibited the presence of a substantial kinetic isotope effect. Addition of benzyltrimethylammonium chloride enhances the reaction rate. It is proposed that the reactive oxidizing species is [PhCH2Me3N]+ [Zn2Cl6]−2I+. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A mechanism involving a hydride-ion transfer from the P-H bond to the oxidant in the rate-determining step has been postulated.

    • 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 the oxidation ofα-hydroxy acids by benzyltrimethylammonium chlorobromate

      Anjana Pradeep K Sharma Kalyan K Banerji

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      The oxidation of glycollic, lactic, malic and a few substituted mandelic acids by benzyltrimethylammonium chlorobromate (BTMACB) in acetic acid-water (1:1) leads to the formation of the corresponding oxoacids. The reaction is of first order in BTMACB as well as the hydroxy acid. Addition of benzyltrimethylammonium chloride or bromide ion does not affect the rate indicating that BTMACB itself is the reactive oxidizing species. The oxidation ofα-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (kH/kD=5·27 at 303 K). The reaction does not exhibit the solvent isotope effect [k(H2O)/k(D2O)=1·01]. The rate decreases with increase in the amount of acetic acid in the solvent mixture. A mechanism is proposed which involves hydride ion transfer to the oxidant.

    • Kinetics and mechanism of the oxidation of some diols by benzyltrimethylammoniumtribromide

      Garima Goswami Seema Kothari Kalyan K Banerji

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      The kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers by benzyltrimethylammonium tribromide (BTMAB) have been studied in 3:7 (v/v) acetic acid-water mixture. The vicinal diols yield the carbonyl compounds arising out of the glycol bond fission while the other diols give the hydroxycarbonyl compounds. The reaction is first-order with respect to BTMAB. Michaelis-Menten type kinetics is observed with respect to diol. Addition of benzyltrimethylammonium chloride does not affect the rate. Tribromide ion is postulated to be the reactive oxidizing species. Oxidation of [1,1,2,2-2H4] ethanediol shows the absence of a kinetic isotope effect. The reaction exhibits substantial solvent isotope effect. A mechanism involving a glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidized by a hydride ion transfer to the oxidant, as are the monohydric alcohols.

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