Reaction kinetics of 2-thiophenesulfonyl chloride with anilines in methanol

The reaction rate constants of 2-thiophenesulfonyl chloride with some substituted anilines have been measured in methanol at different temperatures. The reaction is second order overall and pseudo first order with respect to each reactant. The rate constants value is greater with electron-donating substituents, while it is lower with electron-withdrawing groups. The activation parameters and the slopes of the Hammett (-2.25) and Brønsted (0.53) plots are similar to those of the reaction of benzenesulfonyl chloride with anilines, showing that the reaction mechanism is the same for the two substrates, although 2-thiophenesulfonyl chloride reacts more slowly. The Tommila equation points out that the sulfur atom, the reaction center, is less positively charged, and thus less reactive toward nucleophiles, than that of benzenesulfonyl chloride.