N.M.R. study of monofluorobenzene partially oriented in thermotropic liquid crystals

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Abstract
The 1H and 19F N.M.R. spectra, with natural abundance carbon-13 satellites, of monofluorobenzene dissolved in the nematic ZLI 1167 and ZLI 1132 liquid crystals were recorded and analysed. The r α-structure of monofluorobenzene was determined in both solutions. The proton structure was also determined in the nematic Phase IV liquid crystal; it was found to be independent of the liquid crystal solvent. However, significant deformations in the carbon skeleton are observable. The indirect contributions to the 13C-19F dipole-dipole coupling constants were found to be negligible. The analysis of the 19F spectra and 19F-13C satellite spectra yielded the 13C(12C) isotope effects on the 19F chemical shifts. These shifts are comparable with those observed in normal solvents or in the isotropic phase of liquid crystal solutions.