Electrochemical Investigation of the Oxidation of Phenolic Compounds Using Hypervalent Iodine Oxidants

The chemical oxidation of simple phenolic compounds by the hypervalent iodine reagent [hydroxy(tosyloxy)iodo]benzene (HTIB) was investigated using electrochemical and spectroscopic methods. HTIB oxidized phenol and benzenediol isomers hydroquinone (HQ), catechol, and resorcinol to form various quinone structures. HQ and catechol, two compounds that show reversible electrochemical behavior, exhibited simple oxidative chemistry to their respective quinone structures that could be electrochemically reduced at a glassy carbon electrode. An HTIB:compound ratio of 2:1 resulted in the complete chemical oxidation of these model compounds. However, phenol and resorcinol, two compounds that are known to readily foul electrode surfaces upon their electrochemical oxidation, required a 6:1 HTIB:compound ratio to achieve complete chemical oxidation. The oxidation of resorcinol resulted in a compound that could not be electrochemically reduced; however, the oxidation of phenol from HTIB resulted in an electrochemical redox couple that suggested the preferential formation of benzoquinone, with the possibility of some o-quinone also being produced. This work serves as a proof-of-concept method for the possible indirect electrochemical detection of phenolic compounds.