Structure and conformation of N, p-chlorophenylmaleimide in a nematic solvent by proton magnetic resonance

Abstract

PMR studies of N, p-chlorophenylmaleimide in a nematic solvent have been undertaken. The structural and the conformational informations are derived.

The distance-ratios of the phenyl protons show significant distortions from corresponding values in benzene. The data indicate that the molecule has a twisted conformation with C2-symmetry and that an exchange between energetically equivalent conformations takes place. Assuming a rigid conformation the angle b.thetas between phenyl and maleimide moieties is estimated to be 54.5°C.

The data can also be interpreted by an exchange between planar (b.thetas = 0,180) and perpendicular (b.thetas = ±90) conformations. This possibility is discarded on the basis of theoretical considerations of the stability of conformations.