Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/19021
Title: Rate coefficients of the Cl + CH3C(O)OCH3 → HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition-state theory with ab initio and density functional theory reaction paths
Authors: Chow, R
Ng, M
Mok, DKW 
Lee, EPF
Dyke, JM
Issue Date: 2014
Publisher: American Chemical Society
Source: Journal of physical chemistry A, 2014, v. 118, no. 11, p. 2040-2055 How to cite?
Journal: Journal of physical chemistry A 
Abstract: The complex relationship of computed rate coefficients (k's) with different ab initio/DFT and TST levels was studied. The MEPs, gradients, and Hessians of the title reaction were computed using the MP2 and DFT methods. Electronic energies were improved to the UCCSD(T)-F12x/CBS level, and k's were calculated at the TST, CVT, and ICVT levels with various tunnelling corrections. Although computed microcanonical and tunnelling effects are small, computed k TST values are larger than computed kTST/ZCT and k TST/SCT values by 3 orders of magnitude at low temperatures, because computed κ(TST/CAG) values are as small as 6 × 10 -4. In some cases, the maximum of the ΔG/s curves at a certain T is far away from the MEP maximum. This raises the question of the range of s to be considered in a VTST calculation and, of a possible scenario, where no maximum on the ΔG curve can be located and hence a breakdown of VTST occurs. For dual-level direct dynamics calculations, different entropic contributions from different lower levels can lead to computed k's, which differ by more than 1 order of magnitude. Matching computed and experimental k values leads to an empirical barrier of 1.34 kcal mol-1 for the title reaction.
URI: http://hdl.handle.net/10397/19021
ISSN: 1089-5639
DOI: 10.1021/jp5000864
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