The effect of Carbonyl Containing Substituents in the Terminal chains on Mesomorophic Progerties in Aromatic Esters and Thioesters, 2. Acyloxy Groups on the Phenolic End

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Abstract
The effect of replacingk an alkoxy (Y = OR') with an acyloxy (Y=OCOR') group on the phenolic end of the esters: on their mesomorphic properties has been studied. These esters were prepared by esterification of 4-acyloxyphenols with the appropriate acid chloride. The phenols were synthesized by acylation of 4-benzyloxyphenol with either an aliphatic acid or acid chloride followed by catalytic hydrogenolysis of the benzyl group. A comparison of the melting and clearing temperatures of these acyloxy esters with the corresponding known alkoxy ones showed small increases in both these temper-atures for the acyloxy esters. The same types of mcsophases (N. SA, Sc SB) were observed in both series. but the SB, was more favored when Y=OCOR'. The SC, phase was found to occur in the acyloxy series at chain lengths beyond which it disappeared in the alkoxy series. Comparisons werc also made with the mesomorphic properties previously reported for the corresponding alkyl and α-keto esters. Some correlation was observed between increasing dipole moments of these substituents and increasing transition temperatures hut not in the types of mesophases observed. Fewer mesophases were found when the alkyl chain was attached to the benzene ring through a carbon atom than through an oxygen atom.

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