KINETICS AND MECHANISM OF OXIDATION OF PHENOL AND SUBSTITUTED PHENOLS BY AMMONIUM CHLOROCHROMATE IN AQUEOUS ACETIC ACID

The oxidation of phenols by ammonium chlorochromate (ACC) in aqueous acetic acid leads to the formation of corresponding quinones. The reaction is first order with respect to both phenol and ACC and catalysed by hydrogen ion. The rate of oxidation decreases with increase in dielectric constant of solvent indicating ion-dipole interaction. The rate of oxidation decreases with increase in concentration of KCl, which may be due to the formation of reactive species by interaction of Cl- and protonated ACC. The Hammett plot is found to be valid and the correlation between enthalpies and free energies of activation is reasionably linear with an isokinetic temperature 353 K. Similarly Ig A values of all the phenols are optimised corresponding to E-a of phenols through the following equation: Ig A = Ig k(obs) + E-a/2.303 RT.