KINETICS AND MECHANISM OF OXIDATION OF AROMATIC ANILS BY QUINOLINIUM FLUOROCHROMATE (QFC) IN THE PRESENCE OF OXALIC ACID IN AQUEOUS ACETIC ACID MEDIUM

摘要

The kinetics and mechanism of oxidation of some substituted anils by quinolinium fluorochromate,C_9H_7NH[CrO_3F],have been studied in 60% acetic acid-water (v/v) medium in the presence of oxalic acid at constant ionic strength.The reaction has been found to be first order with respect to both [oxidant] and [substrate] under pseudo-first order conditions.The reaction is acid catalysed and the effect of [NaClOJ is negligible.With an increase in the amount of acetic acid in its aqueous mixture,the rate increases.A 1:2 stoichiometry has been observed in the oxidation and the reaction did not induce polymerisation of acrylonitrile indicating the absence of free radical mechanism.The various activation parameters are calculated from the Arrhenius plot and a suitable mechanism has been proposed.The effect of various meta and para-substituted anils has been also studied.The deviation of the Hammett plot is noticed,and a concave downward curve is obtained for lg k_(obs) versus a.