The torsional barrier in aromatic carbonyl compounds

Abstract

ΔG‡ Values for the torsional barriers of para-substituted benzaldehydes, protonated para-substituted propiophenones, and various p-methoxyacylbenzenes have been measured by dynamic 13C n.m.r. The regression analysis performed for these and other available 1H and 13C n.m.r. data with a variety of inductive and resonance parameters, allowed us to rationalize the effects of different acyl substituents in terms of steric and electronic contributions.