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Kinetics and mechanism of oxidation of phenethyl alcohols by bromamine-T in acid medium

Abstract

The kinetics of the oxidation of six substituted phenethyl alcohols (X - C6H4 - CH2 - CH2 - OH where X = -H, -Cl, -Br, -CH3, -OCH3 and -NO2) by sodium N-bromo-p-toluenesulphonamide or bromamine-T (BAT) in the presence bf HCl has been studied at 35 degrees C. The reaction rate shows a first order dependence both on the BAT](0) and the H+] and is fractional order with respect to PEA](0) and Cl-]. The change in the ionic strength and dielectric constant of the medium and the addition of reaction product, p-toluenesulphonamide have no effect on the reaction rate. The solvent isotope effect k(1(H2O))/k(1(D2O)) similar or equal to 0.86. Proton inventory studies have been made in H2O-D2O mixtures. The rates satisfactorily correlate with Hammett's LFER. The reaction constant rho has been found to be -3.1 for electron releasing substituents and -0.26 for electron withdrawing groups at 35 degrees C. Activation parameters Delta H-not equal, Delta S-not equal, Delta G(not equal) and logA are calculated by studying the reaction at different temperatures (308-318K). It is seen that Delta H-not equal and Delta S-not equal are linearly related and an isokinetic relationship is observed with beta = 330K, indicating enthalpy to be a controlling factor

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