Kinetic and mechanistic study of the reaction of atomic chlorine with methyl bromide over an extended temperature range

Piety, Charles A.; Soller, Raenell; Nicovich, J. M.; McKee, Michael L.; Wine, P. H.

doi:10.1016/s0301-0104(97)00356-x

Cited by 27 publications

(42 citation statements)

References 46 publications

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“…Especially similar are values of the rate constant derived at room temperature [33–38]. Our calculated value of k (CH 3 Br+Cl) of 4.1×10 −13 cm 3 molecule −1 s −1 at 298 K is close to that of (4.4±0.6)×10 −13 obtained by Sarzyński et al [38], (4.5±0.4)×10 −13 of Gierczak et al [34], (4.6±0.3)×10 −13 of Piety et al [37], and (4.8±0.2)×10 −13 obtained at 303 K by Kambanis et al [36], and value of (4.4±0.6)×10 −13 cm 3 molecule −1 s −1 derived at 295 K by Orlando et al [35]. In addition our value of k (CH 3 Br+Cl) is in good agreement with that of (4.4±0.2)×10 −13 cm 3 molecule −1 s −1 recommended by NASA data evaluation [12] at room temperature.…”

Section: Resultssupporting

confidence: 90%

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

et al. 2012

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Ab initio calculations at the G2 level were used in a theoretical description of the kinetics and mechanism of the hydrogen abstraction reactions from fluoro-, chloro- and bromomethane by chlorine atoms. The profiles of the potential energy surfaces show that mechanism of the reactions under investigation is complex and consists of two - in the case of CH3F+Cl - and of three elementary steps for CH3Cl+Cl and CH3Br+Cl. The heights of the energy barrier related to the H-abstraction are of 8–10 kJ mol−1, the lowest value corresponds to CH3Cl+Cl and the highest one to CH3F+Cl. The rate constants were calculated using the theoretical method based on the RRKM theory and the simplified version of the statistical adiabatic channel model. The kinetic equations derived in this studyandallow a description of the kinetics of the reactions under investigation in the temperature range of 200–3000 K. The kinetics of reactions of the entirely deuterated reactants were also included in the kinetic analysis. Results of ab initio calculations show that D-abstraction process is related with the energy barrier of 5 kJ mol−1 higher than the H-abstraction from the corresponding non-deuterated reactant molecule. The derived analytical equations for the reactions, CD3X+Cl, CH2X+HCl and CD2X+DCl (X = F, Cl and Br) are a substantial supplement of the kinetic data necessary for the description and modeling of the processes of importance in the atmospheric chemistry.

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Section: Resultssupporting

confidence: 90%

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

et al. 2012

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“…Clearly, further studies aimed at measuring absolute yields for channel 1a as a function of wavelength would be useful for further quantifying the role of BrONO 2 photochemistry in controlling stratospheric ozone levels. (16) …”

Section: Resultsmentioning

confidence: 99%

Bromine Nitrate Photochemistry: Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

2002

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A laser flash photolysis-resonance fluorescence technique has been employed to investigate the production of Br, O, and BrO from photodissociation of bromine nitrate (BrONO 2 ) at wavelengths in the range 248-355 nm. The values obtained for the Br atom quantum yields are 0.35 ( 0.08, 0.65 ( 0.14, >0.62 ( 0.11, and 0.77 ( 0.19 at 248, 266, 308 and 355 nm, respectively. The values obtained for the O atom quantum yields are 0.66 ( 0.15, 0.18 ( 0.04, <0.13 ( 0.03, and <0.02 at 248, 266, 308, and 355 nm, respectively. Quantum yields for BrO production were investigated at some of the above wavelengths by converting photolytically generated BrO to Br via the reaction BrO + NO f Br + NO 2 . Measured BrO quantum yields are 0.37 ( 0.12 at 266 nm and 0.23 ( 0.08 at 355 nm. Uncertainties in the above quantum yields are estimates of absolute accuracy at the 95% confidence limit. No evidence for pressure-dependent quantum yields was observed over the range 20-200 Torr in N 2 bath gas. No evidence for temperature-dependent quantum yields was observed either, although only a few experiments were done at temperatures other than room temperature. The above results are considered in conjunction with recently reported NO 3 quantum yields [Harwood; et al. J. Phys. Chem. A 1998, 102, 1309 in order to examine the role of BrONO 2 photochemistry in the catalytic destruction of stratospheric ozone.

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“…Thus, an apparently bimolecular reaction may have pressure-dependent contributions from more complex reaction schemes which affect the overall kinetics as well as the reaction mechanism. 21,22,55,59 At sufficiently high temperatures (related to the RX-Y bond strengths) the adducts possess very short lifetimes and these contributions are negligible. As the temperature is lowered, the adducts are able to survive longer aided by stabilizing collisions, leading to a pressure-dependent rate of their reversible formation.…”

Section: Discussionmentioning

confidence: 99%

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals

et al. 2008

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The gas-phase reaction of atomic chlorine with diiodomethane was studied over the temperature range 273-363 K with the very low-pressure reactor (VLPR) technique. The reaction takes place in a Knudsen reactor at pressures below 3 mTorr, where the steady-state concentration of both reactants and stable products is continuously measured by electron-impact mass spectrometry. The absolute rate coefficient as a function of temperature was given by k = (4.70 +/- 0.65) x 10-11 exp[-(241 +/- 33)/T] cm3molecule-1s-1, in the low-pressure regime. The quoted uncertainties are given at a 95% level of confidence (2sigma) and include systematic errors. The reaction occurs via two pathways: the abstraction of a hydrogen atom leading to HCl and the abstraction of an iodine atom leading to ICl. The HCl yield was measured to be ca. 55 +/- 10%. The results suggest that the reaction proceeds via the intermediate CH2I2-Cl adduct formation, with a I-Cl bond strength of 51.9 +/- 15 kJ mol-1, calculated at the B3P86/aug-cc-pVTZ-PP level of theory. Furthermore, the oxidation reactions of CHI2 and CH2I radicals were studied by introducing an excess of molecular oxygen in the Knudsen reactor. HCHO and HCOOH were the primary oxidation products indicating that the reactions with O2 proceed via the intermediate peroxy radical formation and the subsequent elimination of either IO radical or I atom. HCHO and HCOOH were also detected by FT-IR, as the reaction products of photolytically generated CH2I radicals with O2 in a static cell, which supports the proposed oxidation mechanism. Since the photolysis of CH2I2 is about 3 orders of magnitude faster than its reactive loss by Cl atoms, the title reaction does not constitute an important tropospheric sink for CH2I2.

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Kinetic and mechanistic study of the reaction of atomic chlorine with methyl bromide over an extended temperature range

Cited by 27 publications

References 46 publications

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

Bromine Nitrate Photochemistry: Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals

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Kinetic and mechanistic study of the reaction of atomic chlorine with methyl bromide over an extended temperature range

Cited by 27 publications

References 46 publications

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

Theoretical study of the kinetics of reactions of the monohalogenated methanes with atomic chlorine

Bromine Nitrate Photochemistry: Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH2I2 and the Oxidation Mechanism of CH2I Radicals

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Absolute Rate Coefficient Determination and Reaction Mechanism Investigation for the Reaction of Cl Atoms with CH₂I₂ and the Oxidation Mechanism of CH₂I Radicals