Electrochemical oxidative dimerization of monobrominated phenols and pentabromophenol in methanol-aqueous media

摘要

The electrochemical oxidation of monobrominated phenols (2-bromophenol, 3-bromophenol, 4-bromophenol) and pentabromophenol in methanol-aqueous solutions (1:1 and 9:1, v/v) was studied by cyclic voltammetry on glassy carbon electrode in static and rotating disc arrangement. First oxidation step was followed by dimerization reaction resulting in formation of electroactive species. Products of controlled potential electrolysis of bromophenols on the platinum gauze electrode were analysed by ultra-performance liquid chromatography/time of flight mass spectrometry and by gas chromatography/mass spectrometry. C-C and C-O-C linked dimers were found as the main oxidation products in monobrominated phenols solutions electrolysed under mild conditions. Pentabromophenol provided a dimer with C-O-C linkage. On-line coupling of mass spectrometry with electrochemical flow-through cell (EC/MS) containing platinum working electrode proved formation of dimers in the case of 2-bromophenol and 4-bromphenol.