Hindered rotation in o-toluidine derivatives

Abstract

The barrier to rotation about the Ar–N bond in some o-toluidine derivatives has been studied by nuclear magnetic resonance spectroscopy. The planar N-acyl substituents in the amides are considerably more effective in preventing rotation than N-sulphonyl substituents or the N-t-butyl substituent. The relative magnitudes of these energy barriers are in accord with the most recent evidence concerning the conformational requirements of amides and sulphonamides.