Kinetic Study of the Oxidation of Substituted Benzyl Alcohols by Ethyl Chlorocarbamate

Article abstract of DOI:10.1246/bcsj.61.1767

The kinetics of the oxidation of twenty-four monosubstituted benzyl alcohols by ethyl chlorocarbamate (ECC) have been studied in aqueous acetic acid solution, in the presence of perchloric acid.The main product of the oxidation is the corresponding benzaldehyde.The reaction is first order with respect to the alcohol, ECC, and hydrogen ion.The oxidation of <α,α-D₂>benzyl alcohol indicated a primary kinetic isotope effect, k_H/k_D=5.40 at 298 K.The value of solvent isotope effect, k(H2O)/k(D2O), is 1.85 at 298 K.Addition of ethyl carbamate does not affect the reaction rate. ⁺ has been postulated as the reactive oxidizing species.The rates of oxidation of para- and meta-substituted benzyl alcohols show excellent correlation in Taft's dual substituent parameter equation, with negative reaction constants.The rates of the ortho-substituted compounds correlate well in Charton's equation of inductive, resonance and steric substituent parameters.A mechanism involving simultaneous transfer of a hydride ion from the C-H bond and of a proton from O-H bond to the oxidant is proposed.