期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 126, 期 6, 页码 825-833出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpca.1c09556
关键词
-
资金
- National Natural Science Foundation of China [11627901, 21903064]
The rate constants of H-abstraction reactions from dimethylamine by triplets O and O-2 were theoretically determined using the CVT method. The M08-HX/ma-TZVP method was identified as the best by comparing the results with a gold-standard method. The calculations showed that OH and HO2 were mainly produced through direct abstraction from the C-H bond, and the multistructural torsional anharmonicity and tunneling effects played important roles.
Rate constants of the H-abstraction reactions from dimethylamine (DMA) by triplets O and O-2 are theoretically determined with the canonical variational transition-state theory (CVT). By comparing the barrier heights and reaction energies obtained from different density-functional theory methods to those computed from the gold-standard method CCSD(T)/CBS(T-Q), we identify the M08-HX/ma-TZVP method as the best with a mean unsigned deviation of 1.0 kcal mol(-1). On the basis of the optimized geometries and frequencies with the selected method, the rate constants are calculated using the CVT method combined with the multistructural torsional anharmonicity and small-curvature tunnelling (MS-CVT/SCT) options in the temperature range 200-2000 K. The calculations show that OH and HO2 are mainly produced from the direct abstraction from the C-H bond. The multistructural torsional anharmonicity has a large contribution to the rate constants, and the effects of recrossing and tunneling at the N-site are more important than those at C-site. Additionally, given the formation of reactant complex between DMA and triplet O, the H-abstraction channel is not favored at high pressure. Our calculations with both the Polyrate and MESS codes agree with the reported data within the uncertainty.
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