LINEAR FREE-ENERGY RELATIONSHIPS IN CHROMIUM (VI) OXIDATION OF SOME META- AND PARA SUBSTITUTED PHENOLS IN AQUEOUS-ACID MEDIA: A KINETIC AND MECHANISTIC STUDY

摘要

The kinetics of oxidation of a number of meta- and para- substituted phenols by isonicotinium dichromate(INDC) in the presence of oxalic acid in aqueous acetic acid medium have been investigated. The reaction is first order with respect to oxidant and substrate,but fractional order with respect to both [H+ ] ion and oxalic acid..Exner, ‘s plot gives a straight line with fine correlation co- efficient ,But the Hammett plot gives a curve that is concave down ward instead of a straight line.The observed Hammett plot deviation has been accounted for suitabily.From the kinetic data obtained the activation parameters have been computed using Eyring’ s plot and a suitable mechanism has been proposed. The oxidation product is p-benzoquinone. A suitable rate law is derived.