Effect of binary aqueous-organic solvents on the reaction of p-toluene sulfonyl chloride with benzoic acid(s) in the presence of triethyl amine

Second order rate constants (k2) for the reaction of p-toluenesulfonyl chloride with p-substituted benzoic acid(s) [XC6H4COOH, where X= 4-H, 4-CH3 and 4-NO2] in the presence of triethylamine in binary aqueous- Acetonitrile/Acetone mixed solvent have been determined by conductometric method at 25-40 °C. It was found that the rate decreased with increase of water content in Acetonitrile-water binary system. In acetone-water binary system the rate increases with increase in water content to about 10%, reaches a maximum and then decreases. The change in rate with change in concentration of acetone may be explained by solvation behaviour of acetone. Activation parameter (Ea, ΔH‡, ΔS‡, ΔG‡) are evaluated from the rate data by the usual methods. Influence of solvent properties at microscopic and macroscopic level on the rate is subjected to simple and multiple linear correlations. The log k2 values of binary aqueous-acetone system are correlated with Grunwald-Winstein Y values. The ‘m’ value is found to be very low which indicates that the bond breaking and bond making would proceed to the same extent. This is the characteristic property of SN2 reaction.

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