An NMR study of the conformation of glutaric anhydride partially oriented in a nematic solvent

The structural information derived from the dipolar proton-proton couplings in glutaric anhydride is consistent with the sofa-model: only the β-carbon atom is out of the plane of the other ring atoms. With reasonable values of the other internal coordinates the value of the torsional angle between the vicinal cis-protons is between 50 and 53°, which agrees with the value previously determined by Koer et al. The orientation of glutaric anhydride cannot be described by two orientation parameters, which indicates that the reorientational motion is faster than the interconversion between the two sofa-conformations.