Conformational studies of molecules partially oriented in nematic phase: nuclear magnetic resonance and theoretical investigation of 2,2′-bifuryl

The 100 MHz spectra of 2,2′-bifuryl partially oriented in the nematic phase of a liquid crystalline solvent (Merck nematic phase IV) have been obtained and interpreted. The values of direct dipolar couplings Dij show that the molecule exists neither in a single planar form nor in a non-planar one. A number of models taking into account the existence of rapid cis–trans-equilibrium are discussed. It is shown that the O-trans-form is the more stable conformer (78 ± 2%). The hindering internal rotation has been also investigated by means of quantum mechanical calculations using the SCF-MO-LCAO ab initio method. The overall results are compared with previous experimental and theoretical results.