Criegee自由基CH2O2与H2O反应机理及动力学的理论研究

在6-311＋G(2d,2p)水平下, 采用密度泛函理论(DFT)的B3LYP方法, 研究了Criegee 自由基CH₂O₂与H₂O的反应. 结果表明反应存在三个通道: CH₂O₂＋H₂O®HOCH₂OOH (R1); CH₂O₂＋H₂O®HCO＋OH＋H₂O (R2); CH₂O₂＋H₂O®HCHO＋H₂O₂ (R3), 各通道的势垒高度分别为43.35, 85.30和125.85 kJ/mol. 298 K下主反应通道(R1)的经典过渡态理论(TST)与变分过渡态理论(CVT)的速率常数k^TST与k^CVT均为2.47×10^－17 cm³•molecule^－1•s^－1, 而经小曲率隧道效应模型(SCT)校正后的速率常数k^CVT/SCT为 5.22×10^－17 cm³•molecule^－1•s^－1. 另外, 还给出了200～2000 K 温度范围内拟合得到的速率常数随温度变化的三参数Arrhenius方程.

Theoretical Study on the Mechanism and Kinetics of the Reaction of Criegee Radical CH2O2 with H2O

The reaction of Criegee radical CH₂O₂ with H₂O was investigated by density functional theory (DFT) at the B3LYP/6-311G＋(2d,2p) level. Three channels were identified: CH₂O₂＋H₂O®HOCH₂OOH (R1); CH₂O₂＋H₂O®HCO＋OH＋H₂O (R2); CH₂O₂＋H₂O®HCHO＋H₂O₂ (R3). The energy barriers are 43.35, 85.30 and 125.85 kJ/mol for (R1), (R2) and (R3), respectively. The rate constants of reaction (R1) are both 2.47×10^－17 cm³•molecule^－1•s^－1 for classic transitional state theory (TST) k^TST and canonical variational transition state theory (CVT) k^CVT. The rate constant with small-curvature tunneling (SCT) correction k^CVT/SCT is 5.22×10^－17 cm³•molecule^－1•s^－1. The dependence of the rate constants on temperature is given with a three parameters Arrhenius equation within the temperature range 200～2000 K.