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Title: Association rate constants for reactions between resonance-stabilized radicals: C 3H 3 + C 3H 3, C 3H 3 + C 3H 5, and C 3H 5 + C 3H 5

Abstract

Reactions between resonance-stabilized radicals play an important role in combustion chemistry. The theoretical prediction of rate coefficients and product distributions for such reactions is complicated by the fact that the initial complex-formation steps and some dissociation steps are barrierless. In this work, direct variable reaction coordinate transition state theory (VRC-TST) is used to predict accurately the association rate constants for the self and cross reactions of propargyl and allyl radicals. For each reaction, a set of multifaceted dividing surfaces is used to account for the multiple possible addition channels. Because of their resonant nature the geometric relaxation of the radicals is important. Here, the effect of this relaxation is explicitly calculated with the UB3LYP/cc-pvdz method for each mutual orientation encountered in the configurational integrals over the transition state dividing surfaces. The final energies are obtained from CASPT2/cc-pvdz calculations with all π-orbitals in the active space. Evaluations along the minimum energy path suggest that basis set corrections are negligible. The VRC-TST approach was also used to calculate the association rate constant and the corresponding number of states for the C 6H 5 + H → C 6H 6 exit channel of the C 3H 3 + C 3H 3 reaction, whichmore » is also barrierless. For this reaction, the interaction energies were evaluated with the CASPT2(2e,2o)/cc-pvdz method and a 1-D correction is included on the basis of CAS+1+2+QC/aug-cc-pvtz calculations for the CH 3 + H reference system. For the C 3H 3 + C 3H 3 reaction, the VRC-TST results for the energy and angular momentum resolved numbers of states in the entrance channels and in the C 6H 5 + H exit channel are incorporated in a master equation simulation to determine the temperature and pressure dependence of the phenomenological rate coefficients. The rate constants for the C 3H 3 + C 3H 3 and C 3H 5 + C 3H 5 self-reactions compare favorably with the available experimental data. Finally, to our knowledge there are no experimental rate data for the C 3H 3 + C 3H 5 reaction.« less

Authors:
 [1];  [1];  [2]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Chemistry Division
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1426969
Report Number(s):
SAND-2007-1251J
Journal ID: ISSN 1463-9076; PPCPFQ; 526722
Grant/Contract Number:  
AC04-94AL85000; AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 9; Journal Issue: 31; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Georgievskii, Yuri, Miller, James A., and Klippenstein, Stephen J. Association rate constants for reactions between resonance-stabilized radicals: C3H3 + C3H3, C3H3 + C3H5, and C3H5 + C3H5. United States: N. p., 2007. Web. doi:10.1039/B703261G.
Georgievskii, Yuri, Miller, James A., & Klippenstein, Stephen J. Association rate constants for reactions between resonance-stabilized radicals: C3H3 + C3H3, C3H3 + C3H5, and C3H5 + C3H5. United States. doi:10.1039/B703261G.
Georgievskii, Yuri, Miller, James A., and Klippenstein, Stephen J. Fri . "Association rate constants for reactions between resonance-stabilized radicals: C3H3 + C3H3, C3H3 + C3H5, and C3H5 + C3H5". United States. doi:10.1039/B703261G. https://www.osti.gov/servlets/purl/1426969.
@article{osti_1426969,
title = {Association rate constants for reactions between resonance-stabilized radicals: C3H3 + C3H3, C3H3 + C3H5, and C3H5 + C3H5},
author = {Georgievskii, Yuri and Miller, James A. and Klippenstein, Stephen J.},
abstractNote = {Reactions between resonance-stabilized radicals play an important role in combustion chemistry. The theoretical prediction of rate coefficients and product distributions for such reactions is complicated by the fact that the initial complex-formation steps and some dissociation steps are barrierless. In this work, direct variable reaction coordinate transition state theory (VRC-TST) is used to predict accurately the association rate constants for the self and cross reactions of propargyl and allyl radicals. For each reaction, a set of multifaceted dividing surfaces is used to account for the multiple possible addition channels. Because of their resonant nature the geometric relaxation of the radicals is important. Here, the effect of this relaxation is explicitly calculated with the UB3LYP/cc-pvdz method for each mutual orientation encountered in the configurational integrals over the transition state dividing surfaces. The final energies are obtained from CASPT2/cc-pvdz calculations with all π-orbitals in the active space. Evaluations along the minimum energy path suggest that basis set corrections are negligible. The VRC-TST approach was also used to calculate the association rate constant and the corresponding number of states for the C6H5 + H → C6H6 exit channel of the C3H3 + C3H3 reaction, which is also barrierless. For this reaction, the interaction energies were evaluated with the CASPT2(2e,2o)/cc-pvdz method and a 1-D correction is included on the basis of CAS+1+2+QC/aug-cc-pvtz calculations for the CH3 + H reference system. For the C3H3 + C3H3 reaction, the VRC-TST results for the energy and angular momentum resolved numbers of states in the entrance channels and in the C6H5 + H exit channel are incorporated in a master equation simulation to determine the temperature and pressure dependence of the phenomenological rate coefficients. The rate constants for the C3H3 + C3H3 and C3H5 + C3H5 self-reactions compare favorably with the available experimental data. Finally, to our knowledge there are no experimental rate data for the C3H3 + C3H5 reaction.},
doi = {10.1039/B703261G},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 31,
volume = 9,
place = {United States},
year = {2007},
month = {5}
}

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