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Title: Kinetics and thermochemistry of the OH radical reaction with CF{sub 3}CCl{sub 2}H and CF{sub 3}CFClH

Abstract

Rate coefficients are reported for the gas-phase reaction of hydroxyl (OH) radicals with CF{sub 3}CCl{sub 2}H ({kappa}{sub 1}) and CF{sub 3}CFClH ({kappa}{sub 2}) over an extended temperature range. The measurements were performed using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions at a total pressure of 740 {+-} 10 Torr. The lower temperature measurements for {kappa}{sub 1} and {kappa}{sub 2} were in agreement with previous measurements using different techniques. Arrhenius plots of the data exhibit significant curvature and were best described by the following modified Arrhenius expressions (cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, 2{sigma} error limits): {kappa}{sub 1} (296-866 K) = (2.20 {+-} 0.25) x 10{sup {minus}19} T{sup 2.26{+-}0.10} exp({minus}226 {+-} 51)/T and {kappa}{sub 2} (297-867 K) = (7.72 {+-} 0.60) x 10{sup {minus}20} T{sup 2.35{+-}0.06} exp({minus}458 {+-} 30)/T. The experimental measurements were analyzed within the context of transition state theory to provide accurate modified Arrhenius expressions that are applicable to flame conditions. Ab initio calculations were used to evaluate the thermochemical properties of the reactants and products and the partition functions of reactants and their activated complexes. Hydrogen bond dissociation energies (BDE) were also estimated based on calculated enthalpies of formation of reactants and products. An asymmetricalmore » Eckart potential was performed to account for tunneling correction. The resulting TST-based modified Arrhenius expressions (cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}) were {kappa}{sub 1} (250--2,000 K) = 3.25 x 10{sup {minus}21} T{sup 2.88} exp({minus}52/T) and {kappa}{sub 2} (250--2,000 K) = 4.52 x 10{sup {minus}22} T{sup 3.18} exp({minus}362/T). The TST-based modified Arrhenius expression is compared to previous TST and SAR predictions. The results of this study indicate that F substitution at the reaction site has a significant (reductive) effect on hydrochlorofluorocarbon (HCFC) reactivity. This result was also observed in prior studies of CHFCl{sub 2} and CHF{sub 2}Cl. A similar effect in HCFC reactivity was not observed for changes in F substitution {beta} to the reaction site, indicating that the electron-withdrawing effects of the F atoms are limited to the vicinity of the reaction site.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Univ. of Dayton Research Inst., OH (US)
OSTI Identifier:
20075888
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory
Additional Journal Information:
Journal Volume: 104; Journal Issue: 21; Other Information: PBD: 1 Jun 2000; Journal ID: ISSN 1089-5639
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ATMOSPHERIC CHEMISTRY; HALOGENATED ALIPHATIC HYDROCARBONS; HYDROXYL RADICALS; CHEMICAL REACTION KINETICS; ARRHENIUS EQUATION; MATHEMATICAL MODELS

Citation Formats

Yamada, Takahiro, Fang, T.D., Taylor, P.H., and Berry, R.J. Kinetics and thermochemistry of the OH radical reaction with CF{sub 3}CCl{sub 2}H and CF{sub 3}CFClH. United States: N. p., 2000. Web. doi:10.1021/jp993577f.
Yamada, Takahiro, Fang, T.D., Taylor, P.H., & Berry, R.J. Kinetics and thermochemistry of the OH radical reaction with CF{sub 3}CCl{sub 2}H and CF{sub 3}CFClH. United States. doi:10.1021/jp993577f.
Yamada, Takahiro, Fang, T.D., Taylor, P.H., and Berry, R.J. Thu . "Kinetics and thermochemistry of the OH radical reaction with CF{sub 3}CCl{sub 2}H and CF{sub 3}CFClH". United States. doi:10.1021/jp993577f.
@article{osti_20075888,
title = {Kinetics and thermochemistry of the OH radical reaction with CF{sub 3}CCl{sub 2}H and CF{sub 3}CFClH},
author = {Yamada, Takahiro and Fang, T.D. and Taylor, P.H. and Berry, R.J.},
abstractNote = {Rate coefficients are reported for the gas-phase reaction of hydroxyl (OH) radicals with CF{sub 3}CCl{sub 2}H ({kappa}{sub 1}) and CF{sub 3}CFClH ({kappa}{sub 2}) over an extended temperature range. The measurements were performed using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions at a total pressure of 740 {+-} 10 Torr. The lower temperature measurements for {kappa}{sub 1} and {kappa}{sub 2} were in agreement with previous measurements using different techniques. Arrhenius plots of the data exhibit significant curvature and were best described by the following modified Arrhenius expressions (cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, 2{sigma} error limits): {kappa}{sub 1} (296-866 K) = (2.20 {+-} 0.25) x 10{sup {minus}19} T{sup 2.26{+-}0.10} exp({minus}226 {+-} 51)/T and {kappa}{sub 2} (297-867 K) = (7.72 {+-} 0.60) x 10{sup {minus}20} T{sup 2.35{+-}0.06} exp({minus}458 {+-} 30)/T. The experimental measurements were analyzed within the context of transition state theory to provide accurate modified Arrhenius expressions that are applicable to flame conditions. Ab initio calculations were used to evaluate the thermochemical properties of the reactants and products and the partition functions of reactants and their activated complexes. Hydrogen bond dissociation energies (BDE) were also estimated based on calculated enthalpies of formation of reactants and products. An asymmetrical Eckart potential was performed to account for tunneling correction. The resulting TST-based modified Arrhenius expressions (cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}) were {kappa}{sub 1} (250--2,000 K) = 3.25 x 10{sup {minus}21} T{sup 2.88} exp({minus}52/T) and {kappa}{sub 2} (250--2,000 K) = 4.52 x 10{sup {minus}22} T{sup 3.18} exp({minus}362/T). The TST-based modified Arrhenius expression is compared to previous TST and SAR predictions. The results of this study indicate that F substitution at the reaction site has a significant (reductive) effect on hydrochlorofluorocarbon (HCFC) reactivity. This result was also observed in prior studies of CHFCl{sub 2} and CHF{sub 2}Cl. A similar effect in HCFC reactivity was not observed for changes in F substitution {beta} to the reaction site, indicating that the electron-withdrawing effects of the F atoms are limited to the vicinity of the reaction site.},
doi = {10.1021/jp993577f},
journal = {Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory},
issn = {1089-5639},
number = 21,
volume = 104,
place = {United States},
year = {2000},
month = {6}
}