Aromatic amides. X. Anisotropic shielding by protonated amide and thioamide groups

Abstract

N.m.r. spectra have been recorded for solutions of N-aryl amides and thioamides in trifluoroacetic acid. Anisotropic deshielding by >C=O and >C=S is sharply reduced when these groups become protonated and in a number of cases upfield shifts are recorded for nearby protons.