Kinetics of the reaction of tosyl chloride with p-substituted phenol(s) and triethylamine in methanol

The rate constants and activation parameters for the reaction of tosyl chloride with p- substituted phenol(s) - triethylamine in methanol have been determined conductometrically by following the increase in conductance due to the formation of HN+Et3 Cl-,during the course of the reaction. The reaction is second order overall and first order with respect to both substrate and nucleophile. The rate constants are greater for electron donating substituents and lower for electron withdrawing groups in the nucleophile. The substituent effects are correlated by Hammett (ρ = - 0.777) and Bronsted (β = -0.667) equations respectively. The results are compared with the corresponding data for the reaction of tosyl chloride with p- substituted benzoic acid(s)- triethylamine reaction, reported in the literature. The kinetic results are interpreted as a synchronous direct bimolecular nucleophilic substitution reaction. A linear relationship exists between ΔH# and ΔS # which is indicative of a single mechanism

Author(s): Nagarajan Vembu and Chandrasekaran Arunmozhithevan1

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