CF_2自由基与HNCO反应机理的量子化学研究

Theoretical study of the reaction mechanism for CF_2 radical with HNCO

采用密度泛函理论B3LYP 方法研究了CF2 自由基与HNCO 的反应机理， 并在B3LYP/6-311＋＋G＊＊水平上对反应物、中间体、过渡态进行了全几何参数优化， 通过频率分析和内禀反应坐标（IRC）确定了中间体和过渡态.为了得到更精确的能量值， 又用CCSD（T）/6-311＋＋G＊＊方法计算了在B3LYP/6-311＋＋G＊＊水平优化后的各个驻点的相对能量. 根据统计热力学及用Winger校正的Eyring过渡态理论，利用自编程序，计算不同温度下低势垒反应的平衡常数和速率常数.计算结果表明单重态的CF2 自由基与HNCO 的反应有四条反应通道， 三重态的CF2 自由基与HNCO 的反应有两条反应通道.其中单重态反应通道CF2＋HNCO→1IM1→1TS1→1IM2→1TS2→1IM3→CF2NH＋CO（P1）为主反应通道.三重态反应通道CF2＋HNCO→36IM1→36TS1→36IM2→HCF2＋NCO（3P5）为主反应通道.

The reaction mechanism of CF2 radical with HNCO has been investigated by a B3LYP method of density functional theory, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311＋＋G＊＊ level. To obtain more precise energy result, stationary point energies were calculated at a CCSD （T）/6-311＋＋G＊＊//B3LYP/6-311＋＋G＊＊ level. The intermediates and transition states were confirmed by the results of vibrational analysis and the Intrinsic Reaction Coordinates （IRC） calculation. In temperature range of 100 to 2300 K, the statistical thermodynamics and Eyring transition state theory with Winger correction are used to study the thermodynamic and kinetic characters of the channel with low energy barrier at 1.0 Atm. The reaction CF2＋HNCO→1IM1→1TS1→1IM2→1TS2→1IM3→CF2NH＋CO（P1） was the main pathway with larger equilibrium constant and higher rate constant, CF2NH and CO was the main products.