Steric hindrance in the reaction of aromatic sulphonyl chlorides with anilines. Effect of 2-methyl and 2,6-dimethyl substituents in aniline

Abstract

The rates of reaction in methanol of substituted benzenesulphonyl chlorides with anilines are retarded by ortho-methyl substituents in the aniline. The rates for 2-methyl- and 2,6-dimethyl-aniline deviate from the Brønsted plot established by 3- and 4-substituted anilines. This is attributed to a steric effect. The steric effect, which is a function of the electron-withdrawing power of the substituents in the sulphonyl chloride, decrease in the series p-NO2 < p-l < p-Me < p-MeO. This is consistent with the idea that the transition state becomes looser with electron-donating substituents in the sulphonyl chloride.