Abstract
In order to ascertain the effect of heterocyclic rings on liquid crystal stability, a series of Schiff bases derived from 4′-methoxy-4-biphenylamine and aromatic heterocyclic aldehydes has been prepared. The ability of each compound to form a liquid crystal phase, either by melting the crystal or cooling the isotropic liquid, has been determined, and the appropriate heat of transition and corresponding entropy change have been measured by differential scanning calorimetry. The results will be discussed in terms of geometrical considerations, substituent effects, and intermolecular interactions.
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Footnotes
G. W. Gray, Molecular Structure and the Properties of Liquid Crystals ( Academic Press, New York, 1962 ).
Several heterocyclic mesomorphic materials have been reported. See, for example, Reference 1, p. 157.
L. F. Trefilova and I. Y. Postovskii, Doklady Akad. Nauk S.S.S.R., 114, 116 (1957).
Reference 1, pp. 131–133.
We are indebted to Prof. G. W. Gray for providing his synthetic scheme.
F. F. Blicke and O. J. Weinkauff, J. Am. Chem. Soc., 54, 330 (1932).
B. Jones and J. Chapman, J. Chem. Soc., 1952, 1829.
G. W. Gray and B. Jones, ibid., 1954, 1467.
G. W. K. Cavill and D. H. Solomon, ibid., 1955, 1404.
C. Ivanov and I. Panaiotov, Doklady Akad. Nauk S.S.S.R., 93, 1041 (1953).
Compound I has a reported nematic range of 174–176° (Reference 1, p. 133). Compound X is a monotropic nematic liquid crystal’. Compound XI has a reported melting point of 126–127° (Reference 3). The authors are unaware of reports concerning the remainder of the Schiff bases listed in Table I. C = crystal, N = nematic phase, I = isotropic liquid.
Molecular shapes for compounds I and VIII-XIII are very similar. No broadening is detected on Dreiding models.
E. M. Barrall, R. S. Porter, and J. F. Johnson, Molec. Crystals, 3, 299 (1968).
E. M. Barrall, R. S. Porter, and J. F. Johnson, J. Phys. Chem., 68, 2810 (1964).
R. M. Acheson, An Introduction to the Chemistry of Heterocyclic Compounds, Second Edition (Interscience Publishers, London, 1967), pp. 63–64, 93, 120.
Reference 1, pp. 161–163.
M. H. Palmer, The Structure and Reactions of Heterocyclic Compounds ( Edward Arnold Ltd., London, 1967 ), p. 255.
N. A. Lange, Editor, Handbook of Chemistry, Ninth Edition (Handbook Publishers, Inc., Sandusky, Ohio, 1956), pp. 1323, 1358.
This aromaticity difference is attributed to sulfur 3-d orbital participation. See Reference 16, p. 257.
Reference 1, pp. 148–155.
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© 1970 Plenum Press, New York
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Young, W.R., Haller, I., Williams, L. (1970). Mesomorphic Properties of the Heterocyclic Analogs of Benzylidene-4-Amino-4′-Methoxybiphenyl. In: Johnson, J.F., Porter, R.S. (eds) Liquid Crystals and Ordered Fluids. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-8214-0_31
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DOI: https://doi.org/10.1007/978-1-4684-8214-0_31
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