Rate Coefficient Measurements and Theoretical Analysis of the OH + (E)-CF3CH═CHCF3 Reaction

Baasandorj, Munkhbayar; Marshall, Paul; Waterland, Robert L.; Ravishankara, A. R.; Burkholder, James B.

doi:10.1021/acs.jpca.8b02771

Cited by 11 publications

(16 citation statements)

References 27 publications

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“…The relative energies of TS1 and TS16 lie significantly below the initial reactants, as is typical to the OH addition to alkenes where the reaction proceeds through a prereactive van der Waals complex. A similar situation is also observed for the reaction of OH addition to the double bond in Z(E)-CF 3 CHCHCF 3 34,36 and Z(E)-CF 3 CHCHF 34 where the computed barrier is well below the reactants. Both TS1 and TS16 are early transition states in which the geometries are reactant-like where the formed C−O bonds of TS1 and TS16 are 2.2 and 2.3 Å, respectively.…”

Section: ■ Results and Discussionsupporting

confidence: 76%

“…It is seen that the rate coefficient calculated in this work has reasonable agreement with the available recent literature data over a temperature range of 250–450 K. The results also indicate that the fitting three-parameter Arrhenius expression somewhat overestimates activation energy (−2.7 kcal mol –1 ) compared to the experimental results (between −0.5 and −0.7 kcal mol –1 ). However, kinetic data obtained from the calculation does predict negative temperature dependence as observed from the experimental results. − The negative temperature dependence prediction is also consistent with OH radical reactions with carbon–carbon double bonds in other C2 and C3 hydrofluoroalkenes. ,− …”

Section: Resultssupporting

confidence: 72%

“…The possible initiation reaction pathways for CF 2 CHF + OH radicals are H atom and F abstraction pathways and OH addition pathways. Previous studies − have shown that the reaction of fluorinated alkenes with OH radicals proceeds through the addition of OH radicals to the double bond of olefins. The addition reaction pathway is highly exothermic and shows lower barrier heights compared to the other pathways, suggesting that they occur readily under atmospheric conditions.…”

Section: Resultsmentioning

confidence: 99%

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Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

2021

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Fluorinated olefins are valued chemicals in industry, especially as heat transfer fluids in refrigeration applications. As these volatile compounds are widely used, they may be released into the atmosphere, and investigation of their reactions in the atmosphere are therefore of importance. The kinetic analysis of the reaction mechanisms of trifluoroethene (CF 2 CHF) with hydroxyl radicals is studied using computational chemistry at the M06-2X level with the 6-311+ +G(2d,d,p) and aug-cc-pVDZ basis sets as well as the composite CBS-QB3 method. Rate coefficients for the proposed mechanisms are calculated using transition state theory (TST) with tunneling corrections. The calculated rate constants for OH addition to CF 2 CHF are in excellent agreement with experimental values. Kinetic parameters as a function of temperature and pressure are evaluated for the chemically activated formation and unimolecular dissociation of hydroxylfluoroalkyl intermediates. Important forward reactions result in adduct stabilization, H atoms, hydrogen fluoride (HF) via molecular elimination, and formation of fluorinated carbonyl radicals with CF 2 (O) and CHF(O) product channels. Stabilization of initial adducts along with HF elimination are important reaction pathways under high pressure and low temperatures. Important HF eliminations and H atom transfers primarily involve H atoms from the hydroxyl group, as the C−H bonds on or adjacent to carbons with F atoms are stronger and show high barriers to H atom transfer.

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Section: ■ Results and Discussionsupporting

confidence: 76%

Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

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Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

2021

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“…The positive rate coefficient temperature dependence observed in our work for an OH addition reaction is not unprecedented for hydrofluoroolefins and perfluorolefins. , It has been argued that a small energy barrier to the reaction is sufficient to account for such a weak positive temperature dependence …”

Section: Discussionmentioning

confidence: 51%

Atmospheric Chemistry of c-C₅HF₇ and c-C₅F₈: Temperature-Dependent OH Reaction Rate Coefficients, Degradation Products, Infrared Spectra, and Global Warming Potentials

et al. 2021

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c-C 5 HF 7 (1H-heptafluorocyclopentene) and c-C 5 F 8 (perfluorocyclopentene) are potent greenhouse gases presently used as replacement compounds in Si etching. A thorough understanding of their potential impact on climate and air quality necessitates studies of their atmospheric reactivity, radiative properties, and atmospheric degradation pathways. The predominant atmospheric removal process for these compounds is expected to be via reaction with the OH radical. In this study, rate coefficients, k, for the gas-phase reaction of the OH radical with c-C 5 HF 7 and c-C 5 F 8 were measured over a range of temperatures (242−370 K) and pressures (50−100 Torr, He) using a pulsed laser photolysis−laser-induced fluorescence technique. In addition, a complementary relative rate technique, employing multiple reference compounds, was used to study the reactions between 273 and 372 K at 100 Torr (He) total pressure. Reaction rate coefficients were found to be independent of pressure over this range of conditions with k 1 (296 K) = (4.59 ± 0.10) × 10 −14 cm 3 molecule −1 s −1 and k 1 (T) = (4.00 ± 0.40) × 10 −13 exp(−(631 ± 30)/T) cm 3 molecule −1 s −1 for c-C 5 HF 7 and k 2 (296 K) = (4.90 ± 0.14) × 10 −14 cm 3 molecule −1 s −1 and k 2 (T) = (3.59 ± 0.4) × 10 −13 exp(−(591 ± 25)/T) cm 3 molecule −1 s −1 for c-C 5 F 8 . Stable end-products were measured following the OH radical-initiated degradation of c-C 5 HF 7 and c-C 5 F 8 in the presence of O 2 . F(O)CCF 2 CF 2 CF 2 CH(O), CF 2 O, and CO 2 were observed as the major end-products in the oxidation of c-C 5 HF 7 with molar yields of 0.64, 1.27, and 0.53, respectively. For c-C 5 F 8 , F(O)CCF 2 CF 2 CF 2 CF(O), CF 2 O, and CO 2 were observed with molar yields of 0.66, 0.63, and 0.43, respectively. The total carbon mass balance in both systems was 1.0 ± 0.15. The high yield of a C5-dicarbonyl endproduct is consistent with a ring opening at the carbon−carbon double bond site for both c-C 5 HF 7 and c-C 5 F 8 . A comparison of the present kinetic and degradation product results with previously published studies is presented. A rate coefficient upper limit for the gas-phase reaction of O 3 with c-C 5 HF 7 and c-C 5 F 8 of 1 × 10 −21 cm 3 molecule −1 s −1 was measured as part of this work. Atmospheric lifetimes for c-C 5 HF 7 and c-C 5 F 8 are estimated to be 252 and 236 days, respectively. Infrared absorption spectra of c-C 5 HF 7 and c-C 5 F 8 were also measured and found to agree, to within 5%, with results from previous studies. The well-mixed and lifetime adjusted radiative efficiencies (RE, W m −2 ppb −1 ) and 100 year time horizon global warming potential (GWP) for c-C 5 HF 7 are 0.35, 0.24, and 46.7 and for c-C 5 F 8 are 0.38, 0.25, and 46.2, respectively.

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“…Rate coefficients for reaction 1 were measured as a function of temperature (283-374 K) and pressure (50-200 Torr) using a PLP−LIF technique. The apparatus employed in this study has been used previously in our laboratory [21][22][23][24] and is described briefly here. An emphasis in this work was placed on an accurate measurement of the MA concentration.…”

Section: Methodsmentioning

confidence: 99%

Temperature‐dependent rate coefficients for the gas‐phase OH + furan‐2,5‐dione (C₄H₂O₃, maleic anhydride) reaction

Chattopadhyay

Papadimitriou

Marshall

et al. 2020

Int J of Chemical Kinetics

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Rate coefficients, k1(T), for the gas‐phase reaction of the OH radical with furan‐2,5‐dione (maleic anhydride (MA), C4H2O3), a biomass burning related compound, were measured under pseudo–first‐order conditions in OH using the pulsed laser photolysis–laser‐induced fluorescence method over a range of temperature (283‐374 K) and bath gas pressure (50‐200 Torr; He or N2). k1(T) was found to be independent of pressure over this range with k1(283‐374 K) = (1.55 ± 0.20) × 10−12 exp[(−410 ± 44)/T) cm3 molecule−1 s−1 and k1(296 K) = (3.93 ± 0.28) × 10−13 cm3 molecule−1 s−1, where the uncertainties are 2σ and the preexponential term includes the estimated systematic error. The atmospheric lifetime of MA with respect to OH reactive loss is estimated to be ∼15 days. The present results are compared with a previous room temperature relative rate study of the OH + MA reaction, and the significant discrepancy between the studies is discussed; the present results are approximately a factor of 4 lower. It is also noteworthy that the experimentally measured k1(296 K) value obtained in this work is nearly a factor of 110 less than estimated by a structure activity relationship based on trends in ionization potential. Based in part on a computational evaluation, an atmospheric degradation mechanism of MA is proposed.

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Rate Coefficient Measurements and Theoretical Analysis of the OH + (E)-CF₃CH═CHCF₃ Reaction

Cited by 11 publications

References 27 publications

Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

Atmospheric Chemistry of c-C₅HF₇ and c-C₅F₈: Temperature-Dependent OH Reaction Rate Coefficients, Degradation Products, Infrared Spectra, and Global Warming Potentials

Temperature‐dependent rate coefficients for the gas‐phase OH + furan‐2,5‐dione (C₄H₂O₃, maleic anhydride) reaction

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Rate Coefficient Measurements and Theoretical Analysis of the OH + (E)-CF3CH═CHCF3 Reaction

Cited by 11 publications

References 27 publications

Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

Kinetic Analysis of Unimolecular Reactions Following the Addition of the Hydroxyl Radical to 1,1,2-Trifluoroethene

Atmospheric Chemistry of c-C5HF7 and c-C5F8: Temperature-Dependent OH Reaction Rate Coefficients, Degradation Products, Infrared Spectra, and Global Warming Potentials

Temperature‐dependent rate coefficients for the gas‐phase OH + furan‐2,5‐dione (C4H2O3, maleic anhydride) reaction

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Rate Coefficient Measurements and Theoretical Analysis of the OH + (E)-CF₃CH═CHCF₃ Reaction

Atmospheric Chemistry of c-C₅HF₇ and c-C₅F₈: Temperature-Dependent OH Reaction Rate Coefficients, Degradation Products, Infrared Spectra, and Global Warming Potentials

Temperature‐dependent rate coefficients for the gas‐phase OH + furan‐2,5‐dione (C₄H₂O₃, maleic anhydride) reaction