Syntheses of Liquid Crystal Intermediates 4-Alkylbenzenethiols and Phenols

An improved synthesis of 4-alkylbenzenethiols has been developed. Sulfonation of alkyl-benzenes in sulfuric acid at 75° yields 4-alkylbenzene sulfonic acid salts which are free of other positional isomers in high yields. Conversion to the thiols via the sulfonyl chlorides provide a high yield, 3 step synthesis of pure 4-alkylbenzenethiols. Fusion of the salts with potassium hydroxide provides a simple synthetic approach to pure 4-alkylphenols as well. Both the thiols and phenols are useful intermediates in the preparation of mesomorphic compounds.