Substituent effects on oxidation of phenacyl bromides-by manganese(III) sulphate in sulphuric acid and acetic acid media

Abstract

The oxidation of phenacyl bromides by manganese(III) sulphate in acetic acid-sulphuric acid medium is first order each in [phenacyl bromide] and [Mn(HSO₄)²⁺].The reactions are acid-catalysed and participation of water in the reaction is confirmed on the basis of the Hammett's acidity and Bunnett's criteria. The effects of ionic strength and dielectric constant of the medium reveal that the reaction is between a positive ion and dipole. No substituent effect is noticed and isokinetic temperature is evaluated as 297 K which is close to the reaction temperature. A free radical mechanism consistent with the experimental observations is proposed and the activation parameters are reported.