Three compounds with the R–X–Y–CF3 structure were synthesized where X is a trans cyclohexyl ring, Y is a benzene ring and R is an alkyl group. The stuctrure assignments were confirmed by carbon 13 NMR and the compounds were purified by preparative liquid chromatography. The separation of cis and trans isomers of 1-p-trifluorophenyl-4-alkyl-cyclohexonal is also discussed. Although these compounds do not have a liquid crystalline phase themselves, a liquid crystal mixture containing them shows a much faster turn off speed than materials without them.