Kinetics and mechanism of the oxidation of benzyl alcohol to benzaldehyde by acid permanganate

Abstract

The kinetics of the oxidation of benzyl alcohol to benzaldehyde by acid permanganate in the presence of fluoride ions have been studied. The reaction constant ρ for the oxidation of benzyl alcohol and nine substituted benzyl alcohols has a value of –1·76 ± 0·05 at 30 °C. The activation enthalpies and entropies for the ten compounds are linearly related. The oxidation of αα-dideuteriobenzyl alcohol indicated a kinetic isotope effect; k_H/k_D= 2·70 at 30 °C. The reaction does not show any solvent isotope effect. A mechanism involving transfer of a hydride ion from the alcohol carbon to the oxidant is suggested.