136885-27-3Relevant articles and documents
The Synthesis and Mesomorphic Properties of 4-Methyl-Pentyloxyphenylthio-4'-Substituted Benzoates
Neubert, M. E.,Shenouda, I. G.
, p. 29 - 45 (2007/10/02)
Three different series of branched chain alkoxy thioesters of the type p-X-C6H4-C(O)S-C6H4-p-O(CH2)mCH(CH3)(CH2)nCH3 with m = 0-3, n = 3-0; X = R, RO and C9CO2 and R varying between C6 and C12 were synthesized by esterification of 4-substituted benzoic acids with the branched chain alkoxy thiol using the carbodiimide method.Mesomorphic properties were determined by hot-stage polarizing microscopy and compared with those for analogous straight-chain thioesters.Clearing temperatures were always lower in the branched chain than in the straight chain series, but the amount of lowering decreased as the methyl group was moved out along the branched chain away from the benzene ring.Melting temperatures were more variable, as expected, often showing little variation between the 1,2 and 2,1 isomers but increasing considerably for the 3,0 isomer until temperatures were either equal to or slightly higher than those in the straight-chain compounds.The smectic C phase was enhanced usually at the expense of the nematic phase.Nematic-smectic C combinations predominated with the smectic A phase occurring as a short phase range only in the RO-2,1 and X = R series.The most mesophases were usually observed in the 2,1 series; moving the methyl group further out along the chain tended to give restoration of the nematic phase as the predominant phase.The biphenyl thioester p-C8H17O-C6H4-C6H4-C(O)S-C6H4-p-OCH2CH2CH(Me)Et was also synthesized and showed an enantiotropic sequence of SC, SA and N phases with a monotropic smectic G phase which supercooled considerably.Transition temperatures were all > 100 deg C.The thiols with m > 0 were prepared by alkylation of sodium 4-hydroxybenzene-sulfonate with the branched chain bromide, conversion to the sulfonyl chloride and reduction to the thiol.When m = 0, synthesis was by alkylation of 4-bromophenol with the branched chain bromide, treatment with cuprous thiobutane and cleavage of the butyl group with NaNH2.
