Kinetics of chlorination of some Ortho ‐, Meta ‐, and Para ‐substituted phenols by N ‐chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one: A LFER study

The kinetics of chlorination of a number of ortho ‐, meta ‐, and para ‐substituted phenols by N ‐chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one (NCP) in acid medium have been investigated. The reaction is of first order with respect to oxidant and the order with respect to the substrate varies depending on the nature of the substituent present in the ring. With cresols and m ‐chlorophenol the order is unity, with p ‐methoxyphenol, zero and with the other phenols, a fraction. Isokinetic and Exner plots give straight lines with fine correlation coefficients. But the Hammett plot gives a curve that was concave downwards, instead of a straight line. The observed Hammett plot deviation has been accounted for suitably. Regression analyses of the rate data of ortho ‐substituted phenols by using Taft and Charton equations to separate steric effects from electronic effects have been carried out. In this reaction, the localized electronic effect plays a major role while steric and resonance effects play a minor role.