Metal complexes catalyzed oxidative coupling of 2,6-dimethylphenol in micellar media

Abstract

The oxidative coupling reaction of 2,6-dimethylphenol (DMP) with H 2O 2 catalyzed by two copper(II) complexes (2,2′-dipyridylamine copper(II), L 1Cu and N,N′-bis (2-pyridinecarbonyl) ethylenediamine copper(II), L 2Cu) in cationic surfactant cetyl trimethylammonium bromide (CTAB), gemini surfactants ethanediyl-1,2-bis(dodecyldimethylammonium bromide) (12-2-12), dimethylene-1,2-bis(cetyltrimethylammonium bromide) (16-2-16), anionic surfactant sodium dodecyl benzene sulfornate (SDBS) and nonionic surfactant Triton X-100 (TX-100) micellar media were comparatively investigated at 25 °C. The kinetics of formation of 3,3′,5,5′-tetramethyl-4,4′-diphenoquinone (DPQ) was studied. The kinetic parameters k 2 and K m were obtained at pH 7.01. L 1Cu displayed better catalytic activity than L 2Cu in mentioned above systems. For L 1Cu catalyzed systems, the cationic surfactant CTAB, 12-2-12 and 16-2-16 micellar media accelerated the oxidation of DMP. And the TX-100 and SDBS micelles showed little effect on reaction rate compared with the buffer solution. For the L 2Cu catalyzed systems, these surfactants all inhibited the oxidation of DMP, and especially, the oxidation of DMP was not found in SDBS micellar solution in the catalyzed system at pH 7.01 and 25 °C. Micelles showed great influence on the yield of product and the selectivity of PPO. Under this work's conditions, DPQ was easily generated in aqueous solution, while PPO was remarkably promoted in micellar media, especially in SDBS micellar solution. As a green technology process, one outstanding advantage of this catalyzed system was that the products of polymer can be easily separated from the solution and the catalysts still remain in the micellar solution.