Kinetics of elementary radical reactions in the gas phase

Kaufman, F.

doi:10.1021/j150665a024

Cited by 131 publications

(105 citation statements)

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“…The inner wall of the main flow tube was coated with halocarbon wax to minimise any heterogeneous loss of further corrected to allow for deviations from plug-flow as recommended by Kaufman. 19 The diffusion coefficients for Cl atoms and OH radicals in helium were estimated for the pressure of the experiments (between 2.0 and 3.4 Torr) using the diffusion coefficients for Ar and Ne atoms in helium, respectively. The values of the first-order rate constants that were obtained after applying this correction were always within 3% of those obtained without it.…”

Section: Experimental Methodsmentioning

confidence: 99%

Rate constants and Arrhenius parameters for the reactions of OH radicals and Cl atoms with CF3CH2OCHF2, CF3CHClOCHF2 and CF3CH2OCClF2, using the discharge-flow/resonance fluorescence method

Beach

Hickson

Smith

et al. 2001

Phys. Chem. Chem. Phys.

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Rate constants have been determined for the reactions of OH radicals and Cl atoms with the three partially halogenated methyl-ethyl ethers, CF 3 CH 2 OCHF 2 , CF 3 CHClOCHF 2 and CF 3 CH 2 OCClF 2 , using discharge-flow techniques to generate the OH radicals and the Cl atoms and resonance fluorescence to observe changes in their relative concentrations in the presence of added ether. For each combination of radical and ether, experiments were carried out at three temperatures between 292 and 410 K, yielding the following Arrhenius expressions for the rate constants within this range of temperature: OH + CF 3 CH 2 OCHF 2 : k = (2.0 ± 0.8) × 10 -11 exp( -2110 ± 150 K / T) cm 3 molecule -1 s -1 OH + CF 3 CHClOCHF 2 : k = (4.5 ± 1.3) × 10 -13 exp( -940 ± 100 K / T) cm 3 molecule -1 s -1 OH + CF 3 CH 2 OCClF 2 : k = (1.6 ± 0.6) × 10 -12 exp( -1100 ± 125 K / T) cm 3 molecule -1 s -1 Cl + CF 3 CH 2 OCHF 2 : k = (6.1 ± 1.4) × 10 -12 exp( -1830 ± 90 K / T) cm 3 molecule -1 s -1 Cl + CF 3 CHClOCHF 2 : k = (7.8 ± 2.6) × 10 -11 exp( -2980 ± 130 K / T) cm 3 molecule -1 s -1 Cl + CF 3 CH 2 OCClF 2 : k = (2.2 ± 0.2) × 10 -11 exp( -2700 ± 40 K / T) cm 3 molecule -1 s -1 2 Paper for PhysChemChemPhys on OH, Cl + ethersThe results are compared with those obtained previously for the same and related reactions of OH radicals and Cl atoms, and the atmospheric implications of the results are considered briefly. IntroductionPartially halogenated ethers have uses both as potential replacements for chlorofluorocarbons 1 (CFCs) in a number of applications, and as quite widely used anaesthetics. 2 Consequently, studies of the kinetics of the reactions of these compounds with free radicals, especially OH, are useful, since the results aid our understanding of their atmospheric chemistry and allow their atmospheric lifetimes to be estimated. Less directly, they assist with the interpretation of laboratory experiments that are designed to reveal the mechanisms by which these ethers break down in the atmosphere. 3 Finally, evaluation of the rate constants and activation energies for these reactions can help with the construction of structure-activity relationships. In this context, one can, for example, compare the kinetic parameters for the reactions of a given radical with the substituted ethers with those for the reactions of the same radical with the corresponding substituted alkanes where the ether linkage is absent. Alternatively, one can explore how substitution of fluorine or chlorine atoms for hydrogen atoms affects the susceptibility of the molecule to attack by, for example, OH radicals or Cl atoms.Hydrofluoroethers (HFEs) are favoured as possible CFC replacements over other halogenated ethers as they contain no chlorine, which if released as atoms can catalytically destroy stratospheric ozone. Of course, HFEs are volatile and will inevitably be released into the atmosphere during use. Their oxidation, initiated predominantly by OH radicals, will lead to the formation of fluorinated esters and fluorinated formates. 4,5 The likely i...

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Section: Experimental Methodsmentioning

confidence: 99%

Rate constants and Arrhenius parameters for the reactions of OH radicals and Cl atoms with CF3CH2OCHF2, CF3CHClOCHF2 and CF3CH2OCClF2, using the discharge-flow/resonance fluorescence method

Beach

Hickson

Smith

et al. 2001

Phys. Chem. Chem. Phys.

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“…Measurements at different distances along the flow tube yield concentrations at different reaction times. Conversely, a change in flow velocity allows the study of chemical reactions occurring at different rates [120,123]. Spectroscopic detection along the length of the tube, or mass spectrometry using a moveable injector to vary the flow distance, is the most popular detection technique.…”

Section: Slow To Moderately Fast Reactionsmentioning

confidence: 99%

Practical Chemical Kinetics in Solution

Seoud

Baader

Bastos

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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“…This shows that the secondary reactions occurring in the reactor were adequately taken into account. The values of k 1 were also corrected for axial and radial diffusion of OH [20]. The diffusion coefficient of OH in He was calculated from that of O in He [21].…”

Section: Total Rate Constant Of the Oh + Clo Reactionmentioning

confidence: 99%

Kinetics and mechanism of the reaction of OH with ClO

Bedjanian¹,

Riffault²,

Bras³

2001

Int J of Chemical Kinetics

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The kinetics and mechanism of the following reactions have been studied in the temperature range 230-360 K and at total pressure of 1 Torr of helium, using the dischargeflow mass spectrometric method:The following Arrhenius expression for the total rate constant was obtained from the kinetics of OH consumption in excess of ClO radical, produced in the Cl + O 3 reaction either in excess of Cl atoms or ozone: k 1 = (6.7 ± 1.8) × 10 −12 exp{(360 ± 90)/T } cm 3 molecule −1 s −1 (with k 1 = (2.2 ± 0.4) × 10 −11 cm 3 molecule −1 s −1 at T = 298 K), where uncertainties represent 95% confidence limits and include estimated systematic errors. The value of k 1 is compared with those from previous studies and current recommendations. HCl was detected as a minor product of reaction (1) and the rate constant for the channel forming HCl (reaction (1b)) has been determined from the kinetics of HCl formation at T = 230-320 K: k 1b = (9.7 ± 4.1) × 10 −14 exp{(600 ± 120)/T } cm 3 molecule −1 s −1 (with k 1b = (7.3 ± 2.2) × 10 −13 cm 3 molecule −1 s −1 and k 1b /k 1 = 0.035 ± 0.010 at T = 298 K), where uncertainties represent 95% confidence limits. In addition, the measured kinetic data were used to derive the enthalpy of formation of HO 2 radicals: H f,298 (HO 2 ) = 3.0 ± 0.4 kcal mol

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Kinetics of elementary radical reactions in the gas phase

Cited by 131 publications

References 0 publications

Rate constants and Arrhenius parameters for the reactions of OH radicals and Cl atoms with CF3CH2OCHF2, CF3CHClOCHF2 and CF3CH2OCClF2, using the discharge-flow/resonance fluorescence method

Rate constants and Arrhenius parameters for the reactions of OH radicals and Cl atoms with CF3CH2OCHF2, CF3CHClOCHF2 and CF3CH2OCClF2, using the discharge-flow/resonance fluorescence method

Practical Chemical Kinetics in Solution

Kinetics and mechanism of the reaction of OH with ClO

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