Carbon kinetic isotope effects in the gas-phase reactions of light alkanes and ethene with the OH radical at 296 ± 4K

Anderson, R. S.; Iannone, R.; Rudolph, J.; Huang, L.; Thompson, A. E.

doi:10.1021/jp0472008

Journal Article

Carbon kinetic isotope effects in the gas-phase reactions of light alkanes and ethene with the OH radical at 296 ± 4K

Anderson, R. S.FZJ* ; Huang, L. ; Iannone, R.FZJ* ; Thompson, A. E. ; Rudolph, J.FZJ*

2004
Soc. Washington, DC

The journal of physical chemistry <Washington, DC> / A 108, 11537 - 11544 (2004) [10.1021/jp0472008]

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Please use a persistent id in citations: http://hdl.handle.net/2128/768 doi:10.1021/jp0472008

Abstract: The carbon kinetic isotope effects (KIEs) of the room-temperature reactions of several light alkanes and ethene with OH radicals were measured in a 30 L PTFE reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC-IRMS). For simplicity, KIEs are reported in per mil according to epsilon (parts per thousand) = (k(12)/k(13) - 1) x 1000. The following average KIEs were obtained, (all in parts per thousand): ethane, 8.57 +/- 1.95; propane,. 5.46 +/- 0.35; n-butane, 5.16 +/- 0.67; methylpropane, 8.45 +/- 1.49; n-pentane, 2.85 +/- 0.79; methylbutane, 2.91 +/- 0.43; n-hexane, 2.20 +/- 0.07; n-heptane, 1.96 +/- 0.26; n-octane, 2.13 +/- 0.39; cyclopentane, 1.84 +/- 0.13; cyclohexane, 4.46 +/- 0.51; methylcyclopentane, 1.77 +/- 0.53; ethene, 18.6 +/- 2.9. As well, the room-temperature rate constant for the reaction of methylcyclopentane + OH, not previously reported in the literature, was determined using relative rates: (8.6 +/- 2.2) x 10(-12) cm(3) molecule(-1) s(-1), including the estimated 25% uncertainty in the rate constant for cyclopentane + OH. KIE values for propane, n-butane and n-hexane have been reported previously [J. Geophys. Res. [Atmos.] 2000, 105, 29329]. Our KIE for n-hexane is in agreement with the previous measurement, but our values for propane and n-butane are both higher. The dependence between the KIE and chemical structure is discussed, and a method for estimating unknown carbon KIEs for the reactions of light alkanes with OH radicals is presented. With only one exception, predictions using this method agree within a factor of 2 of the experimental KIE results.

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