Mechanism of oxidation of alcohols with N-bromo succinimide

Abstract

The kinetics of the oxidation of a number of aliphatic and aromatic secondary alcohols with N-bromo succinimide has been investigated. Electron-withdrawing substituents retard the reaction considerably and electron-releasing substituents increase the rate of oxidation. The Taft ρ* value is −2.56. Cis- and trans-4-t-butyl cyclohexanols are oxidized at nearly the same rates. There is also a good correlation between the rates of the NBS oxidations and Br2 oxidations of these alcohols. The results are interpreted in terms of a cyclic mechanism involving a rate-determining abstraction of the alpha hydrogen as a hydride anion.