Electrochemical study of quinizarin in the presence of arylsulfinic acids: Synthesis of new sulfone derivatives of quinizarin

Electrochemical oxidation of 1,4-dihydroxyanthraquinone (quinizarin) has been studied in the presence of arylsulfinic acids as nucleophiles in acetonitrile/water mixture by means of cyclic voltammetry as a diagnostic technique. The results indicate that the arylsulfinic acids participate in Michael type addition reaction with the oxidized form of quinizarin, converts it to the corresponding new sulfone derivatives of quinizarin. On the basis of our results, depending on the applied potential, two different series of products are isolated. Furthermore, based on an EC mechanism, the observed homogeneous rate constants (kobs) of the reaction of oxidized form of quinizarin with arylsulfinic acids were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated kobs was found to vary in the order p-toluenesulfinic acid (2a) > benzensulfinic acid (2b) > p-chlorobenzenesulfinic acid (2c).