Mechanistic investigations of the oxidation of phenethyl alcohols by sodium-N-bromo-benzenesulphonamide in acid medium

Abstract

The kinetics of oxidation of six substituted phenethyl alcohols (X-C6H4-CH2-CH2-OH where X=-H, -Cl, -Br, -CH3, -OCH3 and -NO2) by sodium-N-bromo-benzenesulphonamide or bromamine-B(BAB) in the presence of HCl at 35°C showed that the rate has first-order dependence on [BAB]0 and [H+] and fractional order on [PEA]0 and [Cl−]. Ionic strength variations, addition of reaction product of benzenesulphonamide and variation of dielectric constant of the medium have no effect on the rate. The solvent isotope effectk1(H2O)/k1(D2O)⊇0.82. Proton inventory studies have been made in H2O-D2O mixtures. The Hammett plot is biphasic and the reaction constantρ was −3.2 for electron-releasing substituents and −0.34 for electron-withdrawing groups. The activation parameters ΔH#, ΔS# follow an isokinetic relationship.