Linear free energy ortho-correlations in the thiophen series. Part 7. Kinetics of the reaction of some 3-substituted 2-thenoyl chlorides with aniline in benzene

Abstract

The rate constants for the reactions of some 3-substituted 2-thenoyl chlorides (I; X = OMe, Me, SMe, H, I, Br, SOMe, and SO₂Me) with aniline in benzene have been measured. A plot of the logarithm of the rate constants versus the –ΔpK_a values of the corresponding acids furnishes an example of a non-linear free energy relationship, indicating the occurrence of different reaction mechanisms for 2-thenoyl chlorides with, respectively, electron-attracting and -repelling substituents at C-3.