Conformational analysis in heteroaromatic carbonyl compounds. Part II. Nuclear magnetic resonance investigation of thiophen-2,5-dicarbaldehyde in liquid crystals

Abstract

The 100 MHz n.m.r. spectrum of the title compound partially oriented in the nematic phase has been obtained and interpreted. The values of the direct dipolar couplings have been discussed in terms of models which take into account the possibilities of internal rotation rates either faster or slower than the molecular reorientation in the liquid crystals. It is concluded that the molecule exists in the conformations O-cis–cis(70–80%) and O-cis–trans(20–30%), whilst the proportion of the O-trans-trans rotamer is negligible.