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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Chemical Kinetics for Singlet CH2 Reaction with N2 and the Related Decomposition of Diazomethane
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Ab Initio Chemical Kinetics for Singlet CH2 Reaction with N2 and the Related Decomposition of Diazomethane

机译：CH2与N2的单峰CH2反应的从头算化学动力学及重氮甲烷的相关分解

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The kinetics and mechanism for the reaction of singlet state CH2 with N2 have been investigated by ab initio calculations with rate constant prediction. The potential energy surface of the reactions has been calculated by single-point calculations at the CCSD(T)/6-311+G(3df,2p) level based on geometries optimized at the B3LYP/6-311+G(3df,2p) level. By comparing the differences in the predicted heats of reaction with the available experimental values, we estimate the uncertainties in the calculated heats of reactions are (1.4 kcal/mol. Rate constants for various product channels in the temperature range of 300-3000 K are predicted by the variational transition state and RRKM theories. The predicted total rate constants for 1CH2 + N2 at 760 Torr Ar pressure can be represented by the expressions s-ktotal ) 9.67 × 10+7 × T -6.88 exp (-1345/T) cm3 molecule-1 s-1 at T ) 300-2400 K and 3.15 × 10-229 × T +56.18 exp (128 000/T) cm3 molecule-1 s-1 at T ) 2400-3000 K. The branching ratios of the primary channels for 1CH2 + N2 are predicted: k1 for forming singlet s-CH2N2-a (diazomethane) accounts for 0.97-0.01, k2 + k4 for producing HCNN-a + H accounts for 0.00-0.69, k3 for forming singlet s-CH2N2-b (3H-diazirine) accounts for 0.03-0.00, k5 for producing HCN + NH accounts for 0.00-0.18, and k6 for producing CNNH + H accounts for 0.00-0.11 in the temperature range of 300-3000 K. The rate constant predicted for the unimoclecular decomposition of diazomethane producing 1CH2 + N2 agrees closely with experimental results. Because of the low stability of the two isomeric CH2N2 adducts and the high barriers for production of CN-containing products, the contribution of the CH2 + N2 reaction to NO formation becomes very small.
机译：通过从头算和速率常数预测，研究了单重态CH2与N2反应的动力学和机理。根据B3LYP / 6-311 + G（3df，2p）优化的几何结构，通过在CCSD（T）/ 6-311 + G（3df，2p）级别上的单点计算来计算反应的势能面）级别。通过将预测的反应热的差异与可用的实验值进行比较，我们估计计算出的反应热的不确定度为（1.4 kcal / mol。预测了300-3000 K温度范围内各种产物通道的速率常数通过变分过渡态和RRKM理论，在760 Torr Ar压力下1CH2 + N2的预测总速率常数可以用表达式s-ktotal表示：9.67×10 + 7×T -6.88 exp（-1345 / T）cm3 T）300-2400 K时的分子1 s-1和T）2400-3000 K时的3.15×10-229×T +56.18 exp（128 000 / T）cm3分子-1 s-1。预测1CH2 + N2的主要通道：形成单峰s-CH2N2-a（重氮甲烷）的k1占0.97-0.01，产生HCNN-a + H的k2 + k4占0.00-0.69，形成单峰s-CH2N2的k3 -b（3H-diazirine）占0.03-0.00，生产HCN + NH的k5占0.00-0.18，生产CNNH + H的k6占0.00-0.11 i在300-3000 K的温度范围内。预测产生1CH2 + N2的重氮甲烷单分子分解的速率常数与实验结果非常吻合。由于两种异构的CH2N2加合物的稳定性低，并且含CN的产品的生产壁垒很高，因此CH2 + N2反应对NO形成的贡献非常小。

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