Determination of Molecular Structures by Gas Electron Diffraction and NMR Using Liquid-Crystal Solvents

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Molecular structures of some compounds were determined by gas-phase electron diffraction (GED) and NMR using liquid-crystal solvents (LCNMR). The positions of carbon atoms of the solute in liquid crystals were determined from the analysis of the ^<13>C satellites of prot on NMR or ^<13>C-NMR.No ^<13>C-enriched substance was used. 2-and3-Methyl thiophene, 2,5-methyl furan, 4-methyl pyridine and methyl acrylate were studied by LCNMR and GED.Molecular structures of 1,2,3-and 1,3,5-trichlorobenzenes were determined by LCNMR and compared with the gas-phase data reported elsewhere. Most of the bond leghths and angles determined in liquid-crystals are in agreement with those in the gas-phase but one or a few structural parameters are not. In the case of the ring compounds investigated in this work, the molecular deformation tends to decrease by substituting a methyl group for a hydrogen atom of the ring.Molecular structure of t-butyl formate was determined by GED and the (O=) C-O bond was found to increase due to the electron releasing inductive effect. Some interesting structural feature, which can be explained in terms of the difference in the resonance formulas, was found for the gas-phase structures of methyl nicotinate and its isomers, i.e., methyl picolinate and methyl isonicotinate. No experimental data are available for the gas-phase molecular structures of mesogens (compounds forming liquid crystals). The structures of typical mesogens, PAA and MBBA,were determined by GED in this study.