摘要
以Salen-Cu/NaOH/DMF为半乳糖氧化酶的模型,考察了苯甲醇的氧化反应。氧气氛下,笨甲醇被选择性地氧化成苯甲醛,分子氧被还原为H_2O_2。动力学研究结果表明反应对苯甲醇和Salen-Cu均为一级反应,即v=k_表[Salen-Cu][PhCH_2OH],其中k_表=6.1×10^(-3)M^(-1)·min^(-1)。用原位紫外—可见光谱在厌氧和有氧条件下研究了反应过程中d—d跃迁和荷移光谱(MLCT)的变化,结果表明反应诱导过程为Cu(Ⅱ)→Cu(Ⅰ),Cu(Ⅱ)/Cu(Ⅰ)是氧化反应中催化循环的关键,即反应通过两次单电子转移进行。根据实验结果,提出了可能的反应机理。
A model system for the Cu(Ⅱ) metalloenzyme,galactose oxidage, is presented. The Salen-Cu catalyzed the oxidation of benzyl alcohol to benzaldehyde and the leduclion of dioxygen to hydrogen peroxide in DMF containing NaOH at room temperature under 1 atm of O2·The initial rate of the catalytic oxidation was found to be of first order with respect to Cu(Ⅱ) and of first order to benzyl alcohol. The observed rale constant of the oxidation reaction at 25℃and a constant oxygen pressure (1 atm) is 6.1×10-3M-1·min-1. The in-situ visible and UV spectrum studies on d-d transfer and MLCT indicate that the process of induction period is CuⅡ)→Cu(Ⅰ) and that a Cu(Ⅱ)/Cu(Ⅰ) redox cycle is essential for catalysis. A mechanism involving two successive one-electron transfer is proposed.
基金
国家自然科学基金
