Kinetics of base catalysed O-acylation of hydroxamic acids

摘要

The kinetics of 0-acylation of hydroxamic acids using acetic anhydride as an acylating agent in non-aqueous medium,acetonitrile/dioxane has been investigated.The kinetic measurements have been carried out using spectrophotometric technique.The effect of tertiary amines,pyridine/triethylamine on the rate of acylation has been reported.The O-acylation is found to be first order with respect to hydroxamic acids and first order with respect to acetic anhydride.Hence overall order of reaction is found to be two,which is in good agreement with the rate law.The effect of substituents on the rate of acylation,Hammett linear free energy relationship and the thermodynamic parameters are evaluated.The reaction products have been isolated and characterized.The probable mechanism of the acylation is proposed and rate expression is derived.