Restricted rotation. Part 2. Further studies of barriers to rotation in some 3-arycyclohexenone derivatives: effect of substituents on the free energy of activation

Abstract

The free energy of activation for internal rotation about the aryl–cyclohexenone bond in a number of 2-aryl-6-oxocyclohex-1-enylacetic acid derivatives has been determined by dynamic n.m.r. from the coalescence temperature of the AB quartet of the side chain methylene protons. The results are discussed in terms of steric and electronic factors. Chemical shifts of some characteristic groups are correlated with the ground state conformations of the molecules.