A theoretical conformational study of push–pull ethylenes. Part 1. Substituted methyleneimidazolidines

Abstract

Geometries, polarisations, torsional barriers, ionisation potentials, and dipole moments have been computed by MNDO-type calculations for a representative group of ‘push–pull’ ethylenes, formed by an imidazoline ring and a series of acceptor substituents to the double bond, such as cyano, acetyl, and phenyl groups. A relevant number of geometrical parameters was included in the conformational energy optimisation procedure. The comparison with the set of available experimental data allows a rationalisation of the role of π- and strain-energy contributions to the conformational stabilities, and the effect of the withdrawing power of substituents on the height of the barrier.