The University of Southampton
University of Southampton Institutional Repository

Rate coefficients of the Cl + CH3C(O)OCH→ HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition state theory with ab initio and DFT reaction paths

Rate coefficients of the Cl + CH3C(O)OCH→ HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition state theory with ab initio and DFT reaction paths
Rate coefficients of the Cl + CH3C(O)OCH→ HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition state theory with ab initio and DFT reaction paths
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 kTST values are larger than computed kTST/ZCT and kTST/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.
1089-5639
2040-2055
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Lee, Edmond P.F.
f47c6d5d-2d1f-4f03-a3ff-03658812d80b
Mok, Daniel K.W.
49a4e516-0e71-4f59-a3ec-bd607b47ef33
Ng, Maggie
bc203fa1-3eb7-4b63-b1e9-78faca2e5c30
Chow, Ronald
b9dcf296-af75-47d6-b343-c22abaa357c1
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Lee, Edmond P.F.
f47c6d5d-2d1f-4f03-a3ff-03658812d80b
Mok, Daniel K.W.
49a4e516-0e71-4f59-a3ec-bd607b47ef33
Ng, Maggie
bc203fa1-3eb7-4b63-b1e9-78faca2e5c30
Chow, Ronald
b9dcf296-af75-47d6-b343-c22abaa357c1

Dyke, John M., Lee, Edmond P.F., Mok, Daniel K.W., Ng, Maggie and Chow, Ronald (2014) Rate coefficients of the Cl + CH3C(O)OCH→ HCl + CH3C(O)OCH2 reaction at different temperatures calculated by transition state theory with ab initio and DFT reaction paths. Journal of Physical Chemistry A, 118 (11), 2040-2055. (doi:10.1021/jp5000864).

Record type: Article

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 kTST values are larger than computed kTST/ZCT and kTST/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.

Full text not available from this repository.

More information

e-pub ahead of print date: 17 February 2014
Published date: 20 March 2014
Organisations: Chemistry

Identifiers

Local EPrints ID: 362888
URI: http://eprints.soton.ac.uk/id/eprint/362888
ISSN: 1089-5639
PURE UUID: 3b380375-6e27-4053-8dde-54409579f123
ORCID for John M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

Catalogue record

Date deposited: 13 Mar 2014 12:36
Last modified: 03 Dec 2019 02:07

Export record

Altmetrics

Contributors

Author: John M. Dyke ORCID iD
Author: Edmond P.F. Lee
Author: Daniel K.W. Mok
Author: Maggie Ng
Author: Ronald Chow

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×