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Effects of Anharmonicity, Recrossing, Tunneling, and Pressure on the H‑Abstractions from Dimethylamine by Triplets O and O2
dataset
posted on 2022-02-08, 22:14 authored by Yanlei Shang, Hongbo Ning, Jinchun Shi, Yi Wu, Sheng-Nian LuoRate constants of the H-abstraction
reactions from dimethylamine
(DMA) by triplets O and O2 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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reported data withinreaction energies obtainedmess codes agreemean unsigned deviationcanonical variational transition0 kcal mol)/ cbs (functional theory methodsmultistructural torsional anharmonicityh ‑ abstractions2 subcvt method combinedstate theorytzvp methodselected methodtheoretically determinedreactant complexrate constantsq ),optimized geometriesmainly producedlarge contributiondirect abstractiondifferent densitycvt ).curvature tunnellingcalculated usingbarrier heightsabstraction reactionsabstraction channel