Isochoric isothermal pyrolysis of trifluoroiodomethane: CF 3 · recombination kinetics

Скоробогатов, Г. А.; Khripun, V. K.; Rebrova, A. G.

doi:10.1134/s0023158408040022

Cited by 10 publications

(21 citation statements)

References 12 publications

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“…In particular, we cannot explain why there was such a discrepancy between the data (obtained between about 300 and 400 K) of the one group of values near k − 1,∞ ≈ 10 −11 cm 3 molecule −1 s −1 and the other group of lower values such as those given in Table a. However, by combining these data with the two high-temperature determination of refs and , which independently led to k − 1,∞ ≈ 1.5 × 10 −11 cm 3 molecule −1 s −1 (within a factor of 2), one at least can conclude that k − 1,∞ can have only a weak negative or a more or less strong positive temperature coefficient.…”

Section: Experimental Rate Coefficientsmentioning

confidence: 65%

Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

et al. 2010

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Limiting low- and high-pressure rate coefficients as well as full falloff curves have been modeled by unimolecular rate theory for the recombination reaction 2CF(3) (+ M) --> C(2)F(6) (+ M) and the reverse dissociation of C(2)F(6). The results are compared with experimental data from the literature. Although there are considerable discrepancies (up to a factor of 5) between various experimental data near 300 K and the database for high temperatures is still limited, we try to conclude on the temperature dependence of the high-pressure rate coefficient. We suggest that there is only a small and probably positive temperature coefficient of the latter quantity. The present theoretical modeling seems to be in agreement with this experimental result, but it is in disagreement with conclusions from earlier theoretical work. The difference is attributed to different empirical assumptions about the anisotropy of the potential. It is shown that nearly all previous experiments (except high-temperature shock wave and very low pressure pyrolysis/photolysis experiments) correspond to nearly limiting high-pressure conditions.

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Section: Experimental Rate Coefficientsmentioning

confidence: 65%

Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

et al. 2010

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“…Similar to refs − , the present work studied the decomposition of small fluorocarbons in shock waves. It employed absorption spectroscopy in the ultraviolet and visible range for detection.…”

Section: Introductionmentioning

confidence: 79%

“…Quantitative studies of high-temperature fluorocarbon chemistry go back to the work of A. P. Modica and co-workers in the 1960s. − Monitoring absorption signals of CF 2 near 266 nm, the thermal decomposition reactions of CF 3 I, C 2 F 6 , and CF 4 were followed in shock waves, and kinetic as well as thermochemical properties were derived . In the meantime, the dissociations have been investigated in more detail and characterized as unimolecular processes in their falloff regimes (see, e.g., refs − for CF 3 I, refs and for C 2 F 6 , and ref for CF 4 ). A comparison with the corresponding hydrocarbon systems revealed interesting analogies, but also marked differences .…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Fluorocarbon Chemistry Revisited

Cobos

Hintzer²,

Sölter

et al. 2021

J. Phys. Chem. A

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The thermal dissociation reactions of C 2 F 4 and C 2 F 6 were studied in shock waves over the temperature range 1000−4000 K using UV absorption spectroscopy. Absorption cross sections of C 2 F 4 , CF 2 , CF, and C 2 were derived and related to quantum-chemically modeled oscillator strengths. After confirming earlier results for the dissociation rates of C 2 F 4 , CF 3 , and CF 2 , the kinetics of secondary reactions were investigated. For example, the reaction CF 2 + CF 2 → CF + CF 3 was identified. Its rate constant of 10 10 cm 3 mol −1 s −1 near 2400 K is markedly larger than the limiting high-pressure rate constant of the dimerization CF 2 + CF 2 → C 2 F 4 , suggesting that the reaction follows a different path. When the measurements of the thermal dissociation CF 2 (+Ar) → CF + F (+Ar) are extended to temperatures above 2500 K, the formation of C 2 radicals was shown to involve the reaction CF + CF → C 2 F + F (modeled rate constant 8.0 × 10 12 (T/3500 K) 1.0 exp(−4400 K/T) cm 3 mol −1 s −1 ) and the subsequent dissociation C 2 F (+Ar) → C 2 + F + (Ar) (modeled limiting low-pressure rate constant 3.0 × 10 16 (T/3500 K) −4.0 exp(−56880 K/T) cm 3 mol −1 s −1 ). This mechanism was validated by monitoring the dissociation of C 2 at temperatures close to 4000 K. Temperature-and pressure-dependences of rate constants of reactions involved in the system were modeled by quantum-chemistry based rate theory.

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“…The rate coefficients for dissociation of C 2 F 6 were obtained from studies of the reverse recombination of CF 3 radicals between 300 and 1300 K and the equilibrium constant. (See refs – and work cited therein.) For the lowest temperatures of our work, besides the dissociation of C 2 F 6 , the reverse recombination of CF 3 (and other reactions) also had to be taken into account.…”

Section: Experimental Technique and Resultsmentioning

confidence: 99%

Shock Wave Study of the Thermal Decomposition of CF₃ and CF₂ Radicals

et al. 2010

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The thermal dissociation reactions CF(3) + M --> CF(2) + F + M (reaction 1 ) and CF(2) + M --> CF + F + M (reaction 3 ) were studied behind shock waves. CF(2) radicals were monitored through their UV absorption. By working at very low reactant concentrations, the rate coefficients of the unimolecular processes could be derived. Reaction 1 was investigated between 1600 and 2300 K in the intermediate range of the falloff curves, at approximately 10 times larger bath gas pressures than employed in earlier work (Srinivasan, N. K.; Su, M.-C.; Michael, J. V.; Jasper, A. W.; Klippenstein, S. J.; Harding, L. B. J. Phys. Chem. A 2008, 112, 31). The combination of the two sets of data, together with theoretical modeling, allows one to construct falloff curves and to provide complete representations of the temperature and pressure dependences of the rate coefficients. Reaction 3 was studied in the limiting low-pressure range and, over the range 2900-3800 K, a rate coefficient k(3) = [Ar] 1.6 x 10(15) exp(-48,040 K/T) cm(3) molecule(-1) s(-1) was obtained. Representations of the rate coefficients over the full falloff curves were again derived by theoretical modeling.

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Isochoric isothermal pyrolysis of trifluoroiodomethane: CF 3 · recombination kinetics

Cited by 10 publications

References 12 publications

Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

High-Temperature Fluorocarbon Chemistry Revisited

Shock Wave Study of the Thermal Decomposition of CF₃ and CF₂ Radicals

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Isochoric isothermal pyrolysis of trifluoroiodomethane: CF 3 · recombination kinetics

Cited by 10 publications

References 12 publications

Temperature and Pressure Dependence of the Reaction 2CF3 (+ M) ⇔ C2F6 (+ M)

Temperature and Pressure Dependence of the Reaction 2CF3 (+ M) ⇔ C2F6 (+ M)

High-Temperature Fluorocarbon Chemistry Revisited

Shock Wave Study of the Thermal Decomposition of CF3 and CF2 Radicals

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Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

Temperature and Pressure Dependence of the Reaction 2CF₃ (+ M) ⇔ C₂F₆ (+ M)

Shock Wave Study of the Thermal Decomposition of CF₃ and CF₂ Radicals