C2H3与CH3F氢抽提反应机理与动力学性质

采用双水平直接动力学方法对C₂H₃与CH₃F氢抽提反应进行了研究. 在QCISD(T)/6-311++G(d, p)//B3LYP/6-311G(d, p)水平上, 计算的三个反应通道R1、R2和R3的能垒(ΔE^≠)分别为43.2、43.9和44.1 kJ·mol^-1, 反应热为-38.2 kJ·mol^-1. 此外, 利用传统过渡态理论(TST)、正则变分过渡态理论(CVT)和包含小曲率隧道效应(SCT)的CVT, 分别计算了200-3000 K温度范围内反应的速率常数k^TST、k^CVT和k^CVT/SCT. 结果表明: (1) 三个氢抽提反应通道的速率常数随温度的增加而增大, 其中变分效应的影响可以忽略, 隧道效应则在低温段影响显著; (2) R1反应是主反应通道, 但随着温度的升高, R2反应的竞争力增大, 而R3反应对总速率常数的影响很小.

Mechanism and Kinetics of the Hydrogen Abstraction Reaction of C2H3 with CH3F

A dual-level direct dynamics method was employed to study the hydrogen abstraction reaction of C2H3 with CH3F. The calculated potential barriers (ΔE ≠ ) of reaction channels R1, R2, and R3 are 43.2, 43.9, and 44.1 kJ · mol -1 , respectively, and the reaction energy is -38.2 kJ · mol -1 at the QCISD(T)/6-311++ G(d, p)//B3LYP/6-311G(d, p) level. In addition, the rate constants of the reaction were evaluated by means of the conventional transition-state theory (TST) and canonical variational transition-state theory (CVT) with or without small curvature tunneling corrections (SCT) over a wide temperature range of 200-3000 K. The results indicate that the rate constants of the three hydrogen abstraction reaction channels exhibit a positive temperature dependence, in which the variational effect is negligible for all the channels, whereas the tunneling effect is considerable at lower temperatures. Moreover, the reaction R1 is the dominant channel. Reaction R2 competes kinetically with R1 as the temperature increases, whereas the contribution from R3 is small.