• Kalyan K Banerji

      Articles written in Journal of Chemical Sciences

    • Separation of polar and steric effects in the oxidation of ortho-substituted benzaldehydes by N-bromobenzamide

      Kalyan K Banerji

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      The kinetics of the oxidation of twelve ortho-substituted benzaldehydes by N-bromobenzamide (NBB) to the corresponding benzoic acids have been studied. The reaction is first order with respect to NBB, the aldehyde and hydrogen ions. The addition of benzamide has no effect on the reaction rate. (PhCONH2Br)+ has been postulated as the reactive oxidising species. The correlation of rates with the single substituent-parameter equations is poor. The correlation with Charton’s equation of inductive, resonance and steric parameters is satisfactory. However, excellent correlations were obtained, when Charton’s steric parameter was used along with Taft’s σ1; andσR+ substituent constants. The polar reaction constants have negative values. The reaction is subject to steric hindrance by the ortho-substituents.

    • 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 oxidation of phosphorus oxyacids by pyridinium hydrobromide perbromide

      Seema Varshney Pradeep K Sharma Kalyan K Banerji

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      Oxidation of three lower oxyacids of phosphorus, viz. phosphinic, phenylphosphinic and phosphorous acids by pyridinium hydrobromide perbromide (PHPB), is first-order with respect to both oxyacid and PHPB. There is no effect on addition of acylonitrile and pyridinium bromide. On oxidation, deuterated phosphinic and phosphorous acids exhibit substantial kinetic isotope effects. The effect of solvent composition on reaction rate indicates that the transition state is more polar than the reactants. Reaction rates were determined at different temperatures and the activation parameters calculated. Alternative mechanisms, involving the two tautomeric forms of the oxyacid, have been formulated and it has been concluded that the reaction proceeds through the pentacoordinated tautomer. Transfer of a hydride ion from the oxyacid to PHPB, in the rate-determining step, has been proposed.

    • Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

      Madhu Khurana Pradeep K Sharma Kalyan K Banerji

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      Kinetics and mechanism of oxidation of formic and oxalic acids by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is carbon dioxide. The reaction is first-order with respect to QFC. Michaelis-Menten type of kinetics were observed with respect to the reductants. The reaction is acid-catalysed and the acid dependence has the form: kobs =a +b[H+]. The oxidation of α-deuterioformic acid exhibits a substantial primary kinetic isotope effect (kH/kD = 6.01 at 303 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft’s and Swain’s multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate-determining step. Suitable mechanisms have been proposed.

    • Kinetics and mechanism of the oxidation of substituted benzylamines by cetyltrimethylammonium permanganate

      Raghvendra Shukla Pradeep K Sharma László Kótai Kalyan K Banerji

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      Oxidation of meta- and para-substituted benzylamines by cetyltrimethylammonium permanganate (CTAP) to the corresponding aldimines is first order with respect to both the amine and CTAP. Oxidation of deuteriated benzylamine (PhCD2NH2) exhibited the presence of a substantial kinetic isotope effect (kH/kD = 5.60 at 293 K). This confirmed the cleavage of an α-C-H bond in the rate-determining step. Correlation analyses of the rates of oxidation of 19 monosubstituted benzylamines were performed with various single and multiparametric equations. The rates of the oxidation showed excellent correlations in terms of Yukawa—Tsuno and Brown’s equations. The polar reaction constants are negative. The oxidation exhibited an extensive cross-conjugation, in the transition state, between the electron-donating substituents and the reaction centre. A mechanism involving a hydride-ion transfer from the amine to CTAP in the rate-determining step has been proposed.

    • Kinetics and mechanism of the oxidation of some neutral and acidic α-amino acids by tetrabutylammonium tribromide

      Raghvendra Shukla Pradeep K Sharma Kalyan K Banerji

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      The oxidation of eleven amino acids by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid results in the formation of the corresponding carbonyl compounds and ammonia. The reaction is first order with respect to TBATB. Michaelis-Menten type kinetics is observed with some of the amino acids while others exhibit second-order dependence. It failed to induce polymerization of acrylonitrile. The effect of solvent composition indicate that the rate of reaction increases with increase in the polarity of the medium. Addition of tetrabutylammonium chloride has no effect on the rate of oxidation. Addition of bromide ion causes decrease in the oxidation rate but only to a limiting value. The reaction is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed

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