Steric hindrance in the reaction of 2-thiophenesulphonyl chloride with ortho substituted anilines

The rate constants and the activation parameters for the reaction of 2-thiophenesulphonyl chloride with some ortho substituted anilines have been measured in methanol. The rate constant values are always lower than that of aniline. This decreased reactivity can be ascribed to the presence of steric effects, apart from the reaction with o-chloroaniline where the electronic effects of the substituents are remarkable. A further reaction rate decrement is observed for 2,6-disubsituted anilines.The observed rate sequence is ascribed to the combination of polar and steric effects, as shown by the nice correlation of logk/ko values with Pavelich and Taft equation.