Structure of dibenzofuran and dibenzothiophene: Proton NMR study in nematic phases



Proton NMR spectra of dibenzofuran and dibenzothiophene were investigated in the nematic phase of liquid crystals. Dipolar couplings obtained from the spectral analysis were used to derive the inter-proton distance ratios. Deviations from planarity were observed in both molecules, and an attempt was made to determine the extent of non-planarity. Differences in the relative inter-proton distances in the two molecules are explained in terms of the bond polarization hypothesis and the van der Waals and the covalent radii of the oxygen and sulphur heteroatoms.