The electrochemical oxidation of the substituted phenol 2,6-di-t-butylphenol is studied at platinum electrodes using a number of 1-butyl-3-methylimidazolium (bmim) ionic liquids (BF4, PF6 and N(CF3SO2)2), and compared with the oxidation obtained using a traditional solvent/electrolyte system (CH3OH/CH2Cl2 and LiClO4). The electrolysis leads to anodic coupling, resulting in the corresponding diphenoquinone, which upon reduction produces the biphenol. Best results were obtained for the conventional solvent and electrolyte, where the oxidation was found to take place via an indirect method. It was found that the ionic liquids performed better upon dilution with a suitable solvent such as acetonitrile, yielding higher conductivities due to ion separation. Dilution studies were performed with acetonitrile, methanol, dichloromethane and acetone and the resulting increase in conductivity of the ionic liquid was in the order: acetonitrile > methanol > acetone > dichloromethane. This trend is in line with the dielectric constant and the dipole moment of the solvent used. It was found that the electrolysis proceeded best in the following order: conventional solvent/electrolyte > ionic liquid suitably diluted > ionic liquid. Among the ionic liquids, best results were obtained for [bmim][BF4]. Cyclic voltammetry data was used to further explain the electrolysis as a function of dilution.
