Original process for Thymol Para-sulfonation: A Preliminary Optimization Study

In this study, we described an original, new, simple, and productive one-pot method for Thymol para-sulfonation by using thionyl chloride (SOCl 2 ) as a sulfonating agent under mild conditions. Spectroscopic analysis by FT-IR, mass spectrometry, and NMR 1H and 13C confirmed the structure of the parasulfonated derivative of Thymol:  the 4-hydroxy-5-isopropyl-2-methylbenzenesulfonic acid. An optimization study was carried out to perform and improve the yield of this new para-sulfonation method by studying the effect of three parameters: temperature, the molar ratio (η) of the reactants, and solvents. The obtained results showed that the use of cyclohexane as a solvent, a molar ratio greater or equal than 3, and working under low temperatures increase the yield of this parasulfonation considerably to reach adequately 91.3%.