Proton Magnetic Resonance Spectra of Oriented Molecules: Acetylenic Compounds, Acetonitrile and Methanol

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Abstract
The proton magnetic resonance spectra of some acetylenic compounds, acetonitrile and methanol, oriented in the nematic phase of 4, 4-di-n-hexyloxy-azoxy benzene or 4-n-octyloxy-benzoic acid have been investigated. From the chemical shift difference of the signals of the acetylenic proton in the isotropic and nematic phase a value of 12± 1.5 ppm is obtained for the anisotropy of the chemical shift. From the spectra of oriented acetontrile-2−13C and methanol−13C accurate values for the H-C-H bond angle of the methyl groups are derived. The absolute sign of the indirect spin coupling constant J13 CH in acetonitrile-2-13C has been found to be positive.