Structure of pentafluorobenzaldehyde determined from nuclear magnetic resonance spectra of nematic solutions

Abstract

Dipolar coupling constants obtained from an analysis of the n.m.r. spectrum of pentafluorobenzaldehyde dissolved in the nematogen Merck Phase IV have been compared with various models of the equilibrium structure. A normal co-ordinate calculation has been carried out for pentafluorobenzaldehyde in order to allow for vibrational averaging of dipolar couplings. It is concluded that the equilibrium structure is planar with a high barrier to internal rotation of the formyl group.