The relative conformation of ring and chain in ethyl- and n-propyl-benzene studied by nuclear magnetic resonance of liquid crystalline solutions

Abstract

Deuteron n.m.r. spectra and proton spin echo spectra of samples of partially deuteriated ethyl- and propyl-benzene dissolved in liquid crystal solvents have been recorded and analysed. The quadrupolar splittings and dipolar couplings obtained have been used to test two possible minimum-energy conformations for the relative orientations of the ring and alkyl chain. These two conformations are those with C_s symmetry and have the phenyl ring either coplanar or orthogonal to the plane containing the first two carbons in the alkyl group and the carbon in the phenyl ring to which the chain is bonded. The data show unambiguously that neither conformation alone correctly describes the conformational state of these alkylbenzenes.