Temperature-dependent rate constants for the reaction of ground-state chlorine with simple alkanes

Lewis, Roger S.; Sander, Stanley P.; Wagner, S.; Watson, Robert

doi:10.1021/j100453a004

Cited by 93 publications

(53 citation statements)

References 2 publications

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“…This estimation method can therefore be used to calculate room temperature rate constants for the gas-phase reactions of the C1 atom with acyclic and nonstrained cyclic alkanes for which experimental data are not available. Moreover, because the rate constants for the C1 atom reactions with ethane, propane, n-butane, and 2,2-dimethylpropane exhibit only small temperature dependencies [21,23,26,291, the room temperature rate constants can be used for the temperature ranges encountered in the atmosphere with little error.…”

Section: Resultsmentioning

confidence: 99%

Rate constants for the gas‐phase reactions of alkanes with Cl atoms at 296 ± 2 K

Aschmann

Atkinson

1995

Int J of Chemical Kinetics

163

157

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Rate constants for the gas-phase reactions of the C1 atom with a series of alkanes have been determined at 296 t 2 K using a relative rate method. Using a rate constant for the C1 atom reaction with n-butane of 1.94 x cm3 molecule-I s-l, the rate constants obtained (in units of 10-l' cm3 molecule-l s-l) were: 2-methylpentane, 25.0 2 0.8; 3-methylpentane, 24.8 2 0.6; cyclohexane, 30.8 2 1.2; cyclohexane-d12, 25.6 2 0.8; 2,4-dimethylpentane, 25.6 2 1.2; 2,2,3-trimethylbutane, 17.9 2 0.7; methylcyclohexane, 34.7 2 1.2; n-octane, 40.5 2 1.2; 2,2,4-trimethylpentane, 23.1 2 0.8; 2,2,3,3-tetramethylbutane, 15.6 2 0.9; n-nonane, 42.9 t 1.2; n-decane, 48.7 2 1.8; and cis-bicyclo[4.4.0ldecane, 43.1 t 0.8, where the indicated errors are two least-squares standard deviations and do not include the uncertainties in the n-butane rate constant. These data have been combined with rate constants obtained previously for ten C Z -C~ alkanes and this entire data set has been used to develop an estimation method allowing the room temperature rate constants for the reactions of the C1 atom with alkanes to be calculated. 0

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Section: Resultsmentioning

confidence: 99%

Rate constants for the gas‐phase reactions of alkanes with Cl atoms at 296 ± 2 K

Aschmann

Atkinson

1995

Int J of Chemical Kinetics

163

157

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“…Using a different method of approximation, the α radical remains dominant in H-abstraction reactions from tetrahydropyran by OH [14] . Since H-abstraction reactions by Cl are weakly dependent on temperature [15] and pressure [16,17] , the abovementioned branching ratio is assumed similar over the range of experimental conditions herein leading to the expectation that the majority of product formation is largely ascribed to α-tetrahydropyranyl.…”

Section: Initial Radical Distribution From Tetrahydropyran + CL Reactmentioning

confidence: 99%

Influence of oxygenation in cyclic hydrocarbons on chain-termination reactions from R + O2: tetrahydropyran and cyclohexane

Rotavera

Savee

Antonov

et al. 2017

Proceedings of the Combustion Institute

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Multiplexed photoionization mass spectrometry (MPIMS) is used to determine branching fractions of conjugate alkenes from R + O 2 oxidation reactions for cyclohexane ( c -C 6 H 12 ) and tetrahydropyran ( c -C 5 H 10 O), a lignocellulosic-derived oxygenated biofuel. Because conjugate alkene formation is coincident with the formation of HO 2 , the results reveal the temperature-and pressure-dependent influence of the oxygen heteroatom on chain-termination propensity. The experiments were conducted using Cl-initiated oxidation at 10 and 1520 Torr and from 500 to 700 K, and ab initio calculations of bond energies, saddle point energies, and rate coefficients of unimolecular decomposition of α-tetrahydropyranyl were conducted to complement the experiments.Relative to the initial radical concentration [R] 0 the trend in conjugate alkene branching fraction exhibits monotonic positive temperature dependence in both cyclohexane and tetrahydropyran, except for the latter species at 10 Torr where increasing the temperature to 700 K caused an appreciable decrease. The decrease in the branching fraction with increasing temperature in tetrahydropyran oxidation occurs because ring-opening rates of α-tetrahydropyranyl radicals, enabled by weak C-O bond dissociation energies, exceed rates of O 2 -addition. Ring-opening rate coefficients for α-tetrahydropyranyl, computed from stationary points at the CCSD(T)-F12a/cc-PVDZ//M06-2X/6-311 ++ G * * level of theory, confirm that ring-opening at 700 K is favorable and higher oxygen concentrations are required for O 2 -addition rates to be significant. With increased temperature and lower [O 2 ], α-tetrahydropyranyl radicals preferentially undergo unimolecular decomposition into the linear radical ˙ C H 2 ( C H 2 ) 3 CHO . Conjugate alkene branching fractions measured at 1520 Torr for both cyclohexane and tetrahydropyran followed monotonic positive temperature dependence. The change in the tetrahydropyran trend at 1520 Torr relative to the 10 Torr measurements is ascribed to the increase in oxygen concentration mitigating ring-opening reactions of the initial R radicals.In contrast to the results at higher temperature, where ring-opening of tetrahydropyranyl radicals interrupts R + O 2 chemistry and reduces the formation of conjugate alkenes, branching fractions measured below 700 K were higher in tetrahydropyran compared to cyclohexane at 10 Torr. The difference suggests BRotave@Sandia.gov (B. Rotavera), CATaatj@Sandia.gov (C.A. Taatjes). that the ether group renders chain-termination pathways more-facile. Saddle point energy calculations on the surfaces of equatorial ROO conformers reveal that the barrier height to direct HO 2 formation from α-tetrahydropyranylperoxy is lower by ca. 5 kcal/mol compared to cyclohexylperoxy at the CBS-QB3 level of theory, which facilitates low-temperature chain-termination.

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“…In order to verify that kinetic data obtained from HIRAC agree with previous literature recommendations (Atkinson and Aschmann, 1985;Lewis et al, 1980) relative rate techniques were used to measure the kinetics of chlorine atom reactions with propane and isobutane under a variety of conditions. The measurements were carried out at room temperature (298±2 K) and 1000 mbar in N 2 (Dominick Hunter N 2 generator, MAX116, >99.995% purity).…”

Section: Initial Gc Relative Rate Experimentsmentioning

confidence: 76%

Design of and initial results from a highly instrumented reactor for atmospheric chemistry (HIRAC)

Glowacki¹,

Goddard²,

Hemavibool³

et al. 2007

Preprint

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Abstract. The design of a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) is described and initial results obtained from HIRAC are presented. The ability of HIRAC to perform in-situ laser-induced fluorescence detection of OH and HO2 radicals with the Fluorescence Assay by Gas Expansion (FAGE) technique establishes it as internationally unique for a chamber of its size and pressure/temperature variable capabilities. In addition to the FAGE technique, HIRAC features a suite of analytical instrumentation, including: a multipass FTIR system; a conventional gas chromatography (GC) instrument and a GC instrument for formaldehyde detection; and NO/NO2, CO, O3, and H2O vapour analysers. Ray tracing simulations and measurements of the blacklamp flux have been utilized to develop a detailed model of the radiation field within HIRAC. Comparisons between the analysers and the FTIR coupled to HIRAC have been performed, and HIRAC has also been used to investigate pressure dependent kinetics of the chlorine atom reaction with ethene and the reaction of O3 and t-2-butene. The results obtained are in good agreement with literature recommendations and Master Chemical Mechanism predictions. HIRAC thereby offers a highly instrumented platform with the potential for: (1) high precision kinetics investigations over a range of atmospheric conditions; (2) detailed mechanism development, significantly enhanced according to its capability for measuring radicals; and (3) field instrument intercomparison, calibration, development, and investigations of instrument response under a range of atmospheric conditions.

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Temperature-dependent rate constants for the reaction of ground-state chlorine with simple alkanes

Cited by 93 publications

References 2 publications

Rate constants for the gas‐phase reactions of alkanes with Cl atoms at 296 ± 2 K

Rate constants for the gas‐phase reactions of alkanes with Cl atoms at 296 ± 2 K

Influence of oxygenation in cyclic hydrocarbons on chain-termination reactions from R + O2: tetrahydropyran and cyclohexane

Design of and initial results from a highly instrumented reactor for atmospheric chemistry (HIRAC)

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