Analysis of substituent effects: the reactions of some 2-L-5-nitro-3-X-thiophenes with primary and secondary amines in methanol

Abstract

The kinetics of the reactions of some 2-L-5-nitro-3-X-thiophenes with primary and secondary amines in methanol at various temperatures have been studied with the aim of obtaining information about the proximity effects of 3-X ortho-like substituents. The results obtained have shown that for all the substituents considered, except for X = Br, the proximity effects of steric nature are of little relevance with respect to the electronic ones. Thus, it has been possible to establish a set of ortho sigma constants which account well for the electronic effects of 3-X substituents and to obtain excellent linear free energy ortho-correlations.