A facile method for the conversion of certain 9,10-anthraquinones to anthracenes via successive heterogeneous alcoholic sodium borohydride reductions and dehydrations has been developed. Several halo-and methyl-substituted anthracenes have been prepared by this procedure and the intermediate 9,10-dihydroxy-9,10-dihydroanthracenes and enthrones have been isolated and characterized. Ir and nmr spectroscopy have been employed for determination of the isomer distribution of 9,10-dihydroxy-9,10-dihydroanthracenes and unsymmetrically substituted enthrones.
The dielectric anisotropies of a number of terminally substituted Schiff-base and phenyl benzoate liquid crystals are reported. These permittivities are interpreted by use of the Onsager equation for the dielectric behavior of polar liquids. It is demonstrated how the effective dipole moment observed for oriented liquid crystals in fact represents an isotropic contribution as well as the anisotropic contribution, dependent upon the order parameter as previously described by Maier and Meier. Literature values for the group dipole moments are shown to permit quick estimation of the sign and magnitude of the dielectric anisotropy. Group moments, therefore, indicate the relative direction they would have with respect to the remaining structure if one is to optimize the sign and magnitude of the dielectric anisotropy.Liquid crystalline materials are fluids that are anisotropic in their physical properties.1 Their anisotropy occurs spontaneously, usually between the crystalline melting point, Tx, and a higher temperature, Tc, at which the fluid becomes isotropic. Several intermediate phases, or mesophases, may occur beween Tx and Tc; these various phases are classified according to the local symmetry of the anisotropy that the fluid possesses. The mesophase possessing the
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