Aromatic amides. IX. Temperature effects on the N.M.R. spectra of substituted acetanilides

Abstract

N.m.r. spectra have been measured for several anilides in dimethyl sulphoxide solution for temperatures in the range 40-140°. The change of the N-H chemical shift with temperature depends on the nature of the ortho substituent on the benzene ring, being least when a strong intramolecular hydrogen bond is possible between the amide N-H and the ortho substituent. For 2?-nitroanilides, the 6?- proton becomes increasingly deshielded as the temperature is raised.