Studies On Oxidative Coupling Reaction Of 2,6-Dimethylphenol Catalyzed By Copper(Ⅱ) Complexes And Metallomicelles In Aqueous Solution

Four copper(II) complexes were synthesized and the kinetics of oxidative coupling reaction of 2,6-dimethylphenol to 3,3?,5,5?-tetramethyl-4,4?-diphenoquinone(DPQ) with hydrogen peroxide(H2O2) catalyzed by the complexes were studied in Tris-HNO₃ buffer at 25℃. The results showed that the catalytic reactions obeyed Michaelis-Menten enzyme-catalysis kinetics and the kinetic parameters k2 and Km for different conditions were obtained. These complexes show different catalytic activity and optimum pH effects. The copper(II) complexes with both electron conjugated function and appropriate flexibleness in configuration are in favor of the oxidative coupling reaction. The catalytic mechanism was also investigated and the result showed that the reaction was catalyzed mainly by the first acid ionization species of the copper(II) complexes. The analysis by mass spectrum showed that the oxidative coupling reaction of 2,6-dimethylphenol with hydrogen peroxide catalyzed by the complexes generated C-O coupling polymer with different molecular weight. The metallomicelles were applied to the mimetic studies of peroxidase. A copper(â…¡) schiff base complex were synthesized and the kinetics of oxidative coupling reaction of 2,6-dimethylphenol with hydrogen peroxide catalyzed by the complex were investigated in Tris-HNO3 buffer at 25℃. The reaction kinetics was investigated and the kinetic parameters, k2 and Km, were calculated. The study showed the catalytic activity of the copper(â…¡) schiff base complex was better than that of the four copper(II) complexes. The oxidation of 2,6-dimethylphenol was also carried out in CTAB, SDBS and Triton X-100 micellar media at 25℃, respectively. The kinetics of the oxidation of DMP to DPQ was also investigated using enzyme catalysis kinetic model. Before CMC, Triton X-100 enhanced the rate of reaction, however CTAB showed reverse effect. SDBS enhanced the rate of reaction in the range of concentration from 0～3.6×10-4 mol·dm-3 and reduced the rate after its concentration of 3.6×10-4 mol·dm-3. The oxidation of 2,6-dimethylphenol by H2O2 to DPQ were all inhibited by the three micelles. The mechanism of coupling reaction was suggested. The orientation on 2,6-dimethylphenol caused by the electrostatic, hydrophobic and polar effects of the three micelles promotes the C-O coupling route and inhibits the DPQ product. These studies were very important in theory and in application for preparation of functional polymer. The experimental data and studies in this paper provided some useful information for the development of mimetic peroxidase.