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Study of liquid crystalline state of p-n-alkyloxybenzoic acids according to their IR absorption spectra


  1. 1.

    For the three acids investigated (p-n-propyl-, p-n-heptyl-, and p-n-nonyloxybenzoic acids), the existence of a high-temperature solid phase is observed, which is probably the “rotational” α-phase. The identity of the spectra of these acids, taken in the mesophase and in the high-temperature solid phase, indicate a rod-shaped, cylindrical form of the n-alkyl groups of the molecules of these substances in the liquid crystalline state on account of rotation of the molecules around their long axes; the steric properties of such molecules are one of the prerequisities for the formation of a parallel orientation of the molecules in the mesophase.

  2. 2.

    The IR spectra of p-n-cetyloxybenzoic acid, obtained in the liquid crystalline phase, are identical with the spectra obtained in the Isotropic liquid phase. The identity of the spectra indicates the formation of a large number of rotational isomer s of the n-alkyl chain of the molecules in the mesophase, which leads to a disturbanace of the rod-shaped form of the molecule. This lowers the degree of ordering of the molecules in the smectic phase of p-n-cetyloxybenzoic acid in comparison with the ordering of the molecules in the same phase of heptyl- and nonyloxybenzoic acids.

  3. 3.

    In the smectic and nematic phases of p-n-heptyl-and p-n-nonyloxybenzoic acids, the n-alkyl groups of the molecules exist in the same rotational isomeric forms.

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This article is published on the basis of a resolution of the Conference of Editors-in-Chief of the Journals of the Academy of Sciences of the USSR (July 12, 1962) as the dissertation work of V. L. Khodzhaeva.

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2409–2416, November, 1969.

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Khodzhaeva, V.L. Study of liquid crystalline state of p-n-alkyloxybenzoic acids according to their IR absorption spectra. Russ Chem Bull 18, 2257–2262 (1969). https://doi.org/10.1007/BF00906490

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  • Absorption Spectrum
  • Liquid Phase
  • Crystalline Phase
  • Nematic Phasis
  • Liquid Crystalline Phase