An optically active 4-alkylbenzenethiol and an optically active bis(4-alkylphenyl)disulfide represented by the formula: ##STR1## respectively, wherein R.sub.1 * and R.sub.2 * are respectively an alkyl group having 4-12 carbon atoms including an asymmetric carbon atom, may be prepared, e.g., through halogenation or sulfonation of an optically active alcohol, followed by reaction with a phenylmagnesium halide, chlorosulfonylation and reduction. The optically active thiol or disulfide is effective, e.g., in preventing occurrence of reverse domain when added to a nematic liquid crystal, and also can be bonded to an intermediate to provide a functional material including a mesomorphic compound represented by the formula: ##STR2## wherein R.sub.3 is an alkyl or alkoxy group having 1-18 carbon atoms, n is 1 or 2, and C* is an asymmetric carbon atom.