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Bath Gas (bath + gas)

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Chemistry100%

Selected Abstracts

Yet another look at the reaction CH3 + H + M = CH4 + M

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008
David M. GoldenArticle first published online: 10 APR 200
Rate and equilibrium constant parameters for the title system have been evaluated. In general the format used by Baulch et al. (J Phys Chem Ref Data 2005, 34, 757) is compatible with the results. For Ar as the bath gas, the following parameters are suggested: k0 (cm6 molec,2 s,1) = 1.53 × 10,23T,2.17 with Fc = 0.876 exp(,T/1801) + 0.124 exp(,T/33.1). k, = 3.5 × 10,10 cm3 molec,1 s,1 as suggested in Baulch et al. (2005). However, since master equation calculations based on a hindered-Gorin transition state along with an exponential-down energy transfer model (Golden et al., J Phys Chem 2003, 107, 11057,11057) have been carried out herein and compared with data, the results can be stored in lookup tables, avoiding errors introduced by universal expressions, or values can be computed on the fly using the parameters for the master equation calculation given in the paper. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 310,319, 2008 [source]

Kinetics of the gas-phase reaction of n -C6,C10 aldehydes with the nitrate radical

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2003
Jun Noda
Rate coefficients for gas-phase reaction between nitrate radicals and the n -C6,C10 aldehydes have been determined by a relative rate technique. All experiments were carried out at 297 ± 2 K, 1020 ± 10 mbar and using synthetic air or nitrogen as the bath gas. The experiments were made with a collapsible sampling bag as reaction chamber, employing solid-phase micro extraction for sampling and gas chromatography/flame ionization detection for analysis of the reaction mixtures. One limited set of experiments was carried out using a glass reactor and long-path FTIR spectroscopy. The results show good agreement between the different techniques and conditions employed as well as with previous studies (where available). With butanal as reference compound, the determined values (in units of 10,14 cm3 molecule,1 s,1) for each of the aldehydes were as follows: hexanal, 1.7 ± 0.1; heptanal, 2.1 ± 0.3; octanal, 1.5 ± 0.2; nonanal, 1.8 ± 0.2; and decanal, 2.2 ± 0.4. With propene as reference compound, the determined rate coefficients were as follows: heptanal, 1.9 ± 0.2; octanal, 2.0 ± 0.3; and nonanal, 2.2 ± 0.3. With 1-butene as reference compound, the rate coefficients for hexanal and heptanal were 1.6 ± 0.2 and 1.8 ± 0.1, respectively. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 120,129, 2003 [source]

Oxidation of small alkenes at high temperature

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2002
Barbara Heyberger
If the mechanism of formation of alkenes, the main primary products of the combustion of alkanes above 1000 K, is now well understood, their ways of degradation have been much less studied. Following a previous modeling of the oxidation of propene in a static and a jet-stirred reactors by using an automatically generated mechanism, the present paper shows new validations of the same mechanism for ignition delays in a shock tube. It also describes the extension of the rules used for the automatic generation to the case of 1-butene. The predictions of the mechanism produced for the oxidation of 1-butene are compared successfully with two sets of experimental results: the first obtained in a jet-stirred reactor between 900 and 1200 K; the second being new measurements of ignitions delays behind reflected shock waves for temperatures from 1200 up to 1670 K, pressures from 6.6 to 8.9 atm, equivalence ratios from 0.5 to 2, and with argon as bath gas. Flux and sensitivity analyses show that the role of termination reactions involving the very abundant allylic radicals is less important for 1-butene than for propene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 666,677, 2002 [source]

Rate constants for H + CH4, CH3 + H2, and CH4 dissociation at high temperature

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2001
J. W. Sutherland
The Laser Photolysis-Shock Tube technique coupled with H-atom atomic resonance absorption spectrometry has been used to study the reaction, H + CH4 , CH3 + H2, over the temperature range, 928,1697 K. Shock-tube studies on the reverse of this reaction, CH3 + H2 , H + CH4, using CH3I dissociation in the presence of H2 yielded H-atom formation rates and rate constants for the reverse process over the temperature range, 1269,1806 K. These results were transformed (using well-established equilibrium constants) to the forward direction. The combined results for H + CH4 can be represented by an experimental three parameter expression, k = 6.78 × 10,21 T3.156 exp(,4406 K/T) cm3 molecule,1 s,1 (348,1950 K) that was evaluated from the present work and seven previous studies. Using this evaluation, disagreements between previously reported values for the dissociation of CH4 could be reconciled. The thermal decomposition of CH4 was then studied in Kr bath gas. The dissociation results agreed with the earlier studies and were theoretically modeled with the Troe formalism. The energy transfer parameter necessary to explain both the present results and those of Kiefer and Kumaran (J Phys Chem 1993, 97, 414) is, ,,,E,all/cm,1 = 0.3323 T0.7. The low temperature data on the reverse reaction, H + CH3 (in He) from Brouard et al. (J Phys Chem 1989, 93, 4047) were also modeled with the Troe formalism. Lastly, the rate constant for H + CH4 was theoretically calculated using conventional transition state theory with Eckart tunneling corrections. The potential energy surface used was from Kraka et al. (J Chem Phys 1993, 99, 5306) and the derived T-dependence with this method agreed almost perfectly with the experimental evaluation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 669,684, 2001 [source]

Gas-phase reactions of Cl atoms with hydrochloroethers: relative rate constants and their correlation with substituents' electronegativities

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2008
Pablo R. Dalmasso
Abstract Rate constants for the reactions of Cl atoms with CH3OCHCl2 and CH3OCH2CH2Cl were determined at (296,±,2) K and atmospheric pressure using synthetic air as bath gas. Decay rates of these organic compounds were measured relative to the following reference compounds: CH2ClCH2Cl and n -C5H12. Using rate constants of 1.33,×,10,12 and 2.52,×,10,10,cm3,molecule,1,sec,1 for the reaction of Cl atoms with CH2ClCH2Cl and n -C5H12, respectively, the following rate coefficients were derived: k(Cl,+,CH3OCHCl2),=,(1.05,±,0.11),×,10,12 and k(Cl,+,CH3OCH2CH2Cl),=, (1.14,±,0.10),×,10,10, in units of cm3,molecule,1,s,1. The rate constants obtained were compared with previous literature data and a correlation was found between the rate coefficients of some CH3OCHR1R2,+,Cl reactions and ,Electronegativity of CHR1R2. Copyright © 2008 John Wiley & Sons, Ltd. [source]