The Effect of Two Terminal Alkoxy Groups on the Mesomorphic Properties of 4, 4′-Disubstituted Phenylthiobenzoates

Abstract

A select variety of homologs of the dialkoxyphenylthiobenzoates

were prepared. Their mesomorphic properties were determined by hot-stage polarizing microscopy and compared with those for the analogous RO—R’ and R—OR’ thioesters and esters. Unlike the esters, the addition of a second alkoxy group did not give more mesophases than were observed with only one alkoxy group. Only nematic and smeetic C phases were observed with both these phases being enhanced. Several cyclohexane dithioesters of the type

were also prepared. These showed much poorer mesomorphic properties (only short-range monotropic nematic phases) suggesting that the increased number of phases in the RO—R’ thiophenylbenzoates, as compared to the esters, is probably an anomaly rather than a trend.

Most of the 4-alkoxybenzene thiols were prepared by a Newman-Karnes rearrangement of the corresponding phenols, but investigation of the sulfonation of alkoxybenzenes and the alkylation of sodium 4-hydroxybenzene sulfonate indicates that these methods can provide better routes to these thiols.