苯酚羟基化制备苯二酚反应机理的理论研究

采用密度泛函理论(DFT)在UB3L YP／6—311G^**／／UB3LYP／6—31G^*水平上研究了水溶液中羟基自由基进攻苯酚的邻位和对位生成邻苯二酚和对苯二酚的反应机理．结果表明，2个反应都存在3个过渡态，3个中间体，并通过振动分析对过渡态进行了确认．电荷密度的拓扑分析发现，邻位反应中羟基自由基的氧原子和苯酚环上的2个氢原子之间形成了氢键，并相应地形成了六元环和五元环结构．经单点能校正后，2个反应的主反应活化能十分接近，说明邻位和对位产物会同时存在，这与实验观测的结果一致．

Theoretical Studies on Mechanism of Hydroxylation of Phenol for Producing Diphonols

The reaction mechanism of phenol with hydrogen peroxide radical attacking its para and ortho positions in water was proposed and investigated by Density Functional Theory(DFT) method at UB3LYP/6-311G **// UB3LYP/6-31G* computational level. It is found that there are three transition states and three intermediate complexes along each of the reaction path, and the transition states are confirmed through frequency analysis. According to the topological analysis of molecular charge density, it is found in reaction(1), that two hydrogen bonds were formed at the IM1 and TS1, two ring structures(a five- membered ring and a six membered ring) were formed simultaneously. The results of the energy(including single point energy correction and the solvent effect of water) calculation show that the main activation energies of the two reactions are approximately the same, which indicates that both of the two reactions may occur. This is in accordance with the practical experiment that the catechol and hydroquinone both exist in the product mixture.