Evidence of protonation during the oxidation of some aryl alcohols by permanganate in perchloric acid medium and mechanism of the oxidation processes

Abstract

AbstractThe oxidation of benzyl alcohol and methoxy‐, chloro‐, and nitro‐ substituted benzyl alcohols by permanganate has been studied in aqueous and acetic acid medium in presence of perchloric acid. The reaction is first‐order in [MnO4−] and [XC6H4CH2OH], but the order is complex with respect to [H+]. Different thermodynamic parameters have been evaluated. The reaction occurs through the protonation of alcohol in a fast preequilibrium followed by a slow rate‐determining oxidation step. A two‐electron transfer oxidation step has been suggested for benzyl alcohol and chloro‐ and nitro‐ substituted alcohols, while the oxidation of methoxy compounds involves a one‐electron transfer via a free‐radical mechanism. © 1995 John Wiley & Sons, Inc.