摘要:

AbstractThe kinetics of the gas‐phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4over the temperature range 271–363 K. Usingk(Cl + CH4) = 9.6 × 10−12exp(−2680/RT) cm3molecule−1s−1, we derivek(Cl + CF3I) = 6.25 × 10−11exp(−2970/RT) in whichEahas units of cal mol−1. CF3radicals are produced from the reaction of Cl with CF3I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments werek(Cl + C2F5I)/k(Cl + CF3I) = 11.0 ± 0.6 andk(Cl + C2F5I)/k(Cl + C2H5Cl) = 0.49 ± 0.02. The reaction of CF3radicals with Cl2was studied relative to that with O2at pressures from 4 to 700 torr of N2diluent. By using the published absolute rate constants fork(CF3+ O2) at 1–10 torr to calibrate the pressure dependence of these relative rate constants, values of the low‐ and high‐pressure limiting rate constants have been determined at 296 K using a Troe expression:k0(CF3+ O2) = (4.8 ± 1.2) × 10−29cm6molecule−2s−1;k∞(CF3+ O2) = (3.95 ± 0.25) × 10−12cm3molecule−1s−1;Fc= 0.46. The value of the rate constantk(CF3+ Cl2) was determined to be (3.5 ± 0.4) × 10−14cm3molecule−1s−1at 296 K. The reaction of Cl atoms with CF3I is a convenient way to prepare CF3radic

ISSN:0538-8066    

DOI:10.1002/kin.550270302

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe title reaction, a key elementary process involved in the chemistry of molecular clouds, has been theoretically studied over the 5–600 K temperature range. Rate constants calculations have been carried out using the full version of the statistical adiabatic channel model in conjunction with a potential energy surface that has been derived from recent ab initio quantum chemical data. By using various switching functions, the influence of the attenuation of the bound‐complex bending frequency upon NOH bond elongation on the temperature dependence of the reaction was investigated. The rate constants exhibit a slightly positive temperature dependence with a calculated rate constant value at 300 K in very good agreement with the measured value. A comparison with the available experimental data between 250 and 515 K suggests that recrossing trajectories might occur with increasing importance as the temperature increases. However, the nonstatistical recrossing effects are expected to be of minor importance at interstellar temperatures such that the rate constants over the 5–200 K temperature range are given byk= 8.41 × 10−12T+0.30cm3molecule−1s−1. The rate constant calculated at 10 K is consistent with that derived in the astrochemical modeling of the L134N dark cloud. Rate constants for individual quantum states are also presented. © 1995 John

ISSN:0538-8066    

DOI:10.1002/kin.550270303

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experimental study of the kinetics of the B2H6/O (3P) system at room temperature, is presented. Modeling was based on a multiple‐parameter fitting process to a complex kinetic mechanism. The aim of the study was to propose and evaluate a preferred set of elementary reactions which might be important for the oxidation of boron‐hydrides. In this study, relative concentration‐vs.‐time profiles of the radicals OH and BO2were measured in a low pressure flow reactor, by the technique of laser‐induced‐fluorescence. A range of almost two orders of magnitude in the initial fuel to oxygen ratio was covered, while the residence times of the gases in the reactor were up to 1 s. A comprehensive kinetic mechanism was constructed from the available measured and estimated data in literature. After the fitting process and dropping all of the reactions with negligible contribution, a 46 elementary reactions mechanism was obtained. In this mechanism, 27 reactions are not measured and their rate coefficients were used as the adjustable (within reasonable limits deduced from kinetic and thermodynamic considerations) parameters of the fitting process. Good agreement was obtained between all of the measured and calculated profiles. From sensitivity analysis it was found that only a limited group of these reactions highly contributes to the calculated concentrations of OH and BO2. With only the highly contributing reactions and all the oxygenhydrogen reactions which are measured and relatively well known, a 30 elementary reactions mechanism was obtained. In this mechanism only 13 reactions are not measured and the agreement between the measured and the calculated profiles is still reasonable. To demonstrate the possible usefulness of the proposed mechanism, the rate coefficient of the reaction B2H6+ OH → B2H5+ H2O which was not measured before, was directly measured in our experimental set‐up. The rate coefficient that was obtained in the direct measurement is (3.3 ± 1.1) × 1011cm3mol−1s−1, in excellent agreement with the predicted one by the multiple‐parameter‐fitting process, which was 2 × 1011cm3mol−1s−

ISSN:0538-8066    

DOI:10.1002/kin.550270304

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe gas‐phase reactions of the OH radical with 4‐methyl‐2‐pentanone and 2,6‐dimethyl‐4‐heptanone have been investigated in the presence of NOx. Acetone and 2‐methylpropanal were identified and qualified as products of both reactions. The acetone yield from 2,6‐dimethyl‐4‐heptanone increased after addition of NO to reacted mixtures, indicating that acetone is formed through the intermediary of an acyl radical. The acetone and 2‐methylopropanal formation yields were determined to be 0.78 ± 0.06 and 0.071 ± 0.011, respectively, from 4‐methyl‐2‐pentanone and 0.68 ± 0.11 and 0.385 ± 0.034, respectively, from 2,6‐dimethyl‐4‐heptanone. The possible reaction mechanisms are discussed and compared with these product data, and it is concluded that the experimental data provide direct evidence for isomerization of the (CH3)2CHCH2C(O)CH2C(O) (CH3)2alkoxy radical formed from 2,6‐dimethyl‐4‐heptanone. However, the isomerization rates of the alkoxy radicals formed from the ketones depend on whether the H‐atom abstracted is on a carbon atom α or β to the>CO group, with H‐atom abstraction from CH bonds on the β carbon atoms being significantly faster than from C

ISSN:0538-8066    

DOI:10.1002/kin.550270305

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of the reactions of ground state oxygen atoms withtrans‐2‐butene,cis‐2‐butene, 2‐methylpropene, 2‐methyl‐2‐butene, and 2,3‐dimethyl‐2‐butene was investigated in the temperature range 200 to 370K. In this range, the rate constants are (in units 10−11cm3s−1): (1.1 ± 0.1) exp[+(180 ± 24)K/T]; (0.98 ± 0.09) exp[+(149 ± 23)K/T]; (1.14 ± 0.13) exp[+(128 ± 33)K/T]; (2.34 ± 0.16) exp[+(250 ± 16)K/T]; and (3.31 ± 0.50) exp[+(257 ± 36)K/T], respectively. The atoms were generated by the H2laser photolysis of NO and detected by the time resolved chemiluminescence in the presence of NO. The concentrations of the O(3P) atoms were kept so low that secondary reactions with products are unimp

ISSN:0538-8066    

DOI:10.1002/kin.550270306

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe temperature dependence of the rate coefficients for the OH radical reactions with toluene, benzene,o‐cresol,m‐cresol,p‐cresol, phenol, and benzaldehyde were measured by the competitive technique under simulated atmospheric conditions over the temperature range 258–373 K. The relative rate coefficients obtained were placed on an absolute basis using evaluated rate coefficients for the corresponding reference compounds. Based on the rate coefficientk(OH + 2,3‐dimethylbutane) = 6.2 × 10−12cm3molecule−1s−1, independent of temperature, the rate coefficient for toluenekOH= 0.79 × 10−12exp[(614 ± 114)/T] cm3molecule−1s−1over the temperature range 284–363 K was determined. The following rate coefficients in units of cm3molecule−1s−1were determined relative to the rate coefficientk(OH + 1,3‐butadiene) = 1.48 × 10−11exp(448/T) cm3molecule−1s−1:o‐cresol;kOH= 9.8 × 10−13exp[(1166 ± 248)/T]; 301–373 K;p‐cresol;kOH= 2.21 × 10−12exp[(943 ± 449)/T]; 301–373 K; and phenol,kOH= 3.7 × 10−13exp[(1267 ± 233)/T]; 301–373 K. The rate coefficient for benzaldehydekOH= 5.32 × 10−12exp[(243 ± 85)/T], 294–343 K was determined relative to the rate coefficientk(OH + diethyl ether) = 7.3 × 10−12exp(158/T) cm3molecule−1s−1. The data have been compared to the available literature data and where possible evaluated rate coefficients have been deduced or updated. Using the evaluated rate coefficientk(OH + toluene) = 1.59 × 10−12exp[(396 ± 105)/T] cm3molecule−1s−1, 213–363 K, the following rate coefficient for benzene has been determinedkOH= 2.58 × 10−12exp[(−231 ± 84)/T] cm3molecule−1s−1over the temperature range 274–363 K and the rate coefficent form‐cresol,kOH= 5.17 × 10−12exp[(686 ± 231)/T] cm3molecule−1s−1, 299–373 K was determined relative to the evaluated rate coefficientk(OH +o‐cresol) = 2.1 × 10−12exp[(881 ± 356)/T] cm3molecule−1s−1. The tropospheric lifetimes of the aromatic compounds studied were calculated relative to that for 1,1,1‐tricloreth

ISSN:0538-8066    

DOI:10.1002/kin.550270307

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractRevised values are given for the rate coefficients of ethane and methane decomposition derived from the laser absorption shock tube measurements performed by Davidson et al. (1992, 1993). This revision results from a reassessment of the methyl absorption coefficient used in the original studies. © 1995 John Wiley&Sons, Inc

ISSN:0538-8066    

DOI:10.1002/kin.550270308

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550270309

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550270301

出版商:John Wiley&Sons, Inc.    

年代:1995

数据来源: WILEY