摘要:

AbstractAbsolute rate constants for H‐atom abstraction by OH radicals from cyclopropane, cyclopentane, and cycloheptane have been determined in the gas phase at 298 K. Hydroxyl radicals were generated by flash photolysis of H2O vapor in the vacuum UV, and monitored by time‐resolved resonance absorption at 308.2 nm [OH(A2Σ+→X2Π)]. The rate constants in units of cm3mol−1s−1at the 95% confidence limits were as follows:k(cC3H6) = (3.74 ± 0.83) × 1010,k(cC5H10) = (3.12 ± 0.23) × 1012,k(cC7H14) = (7.88 ± 1.38) × 1012. A linear correlation was found to exist between the logarithm of the rate constant per CH bond and the corresponding bond dissociation energy for several classes of organic compounds with equivalent CH bonds. The correlation favors a value of D(cC

ISSN:0538-8066    

DOI:10.1002/kin.550170102

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractRecent interest in the measurement and the interpretation of heat capacities of activation has led to more rigorous methods to detect temperature‐varient activation parameters. One such method devised by Blandamer and co‐workers was applied to the sucrose hydrolysis data of Moelwyn‐Hughes and Leininger and Kilpatrick. Both sets of investigators claimed that the energy of activation for sucrose inversion decreased with increasing temperature, while Heidt and Purvis and more recently, Kuhler's group contend that the energy of activation is constant. It was found that neither the data of Moelwyn‐Hughes nor of Leininger and Kilpatrick warrant the inclusion of a temperature‐dependent activation

ISSN:0538-8066    

DOI:10.1002/kin.550170103

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe reactionhas been studied using a discharge‐flow tube with resonant fluorescence detection of HO. Measurements ofk1have been made at temperatures between 237 and 404 K. Our results and earlier work suggest that the rate constant has a minimum atT≃ 500 K. Below room temperature our results are given by the expressionk= (2.0 ± 0.4) × 10−14exp[(430 ± 60)/T] cm3molecule−1s−1, where the error limits include an estimate of the measurement accuracy. No dependence ofk1on pressure at 300 K is observed in studies between 1‐ and 10‐torr helium. An upper limit ofkb<1%k1a

ISSN:0538-8066    

DOI:10.1002/kin.550170104

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractUsing a relative rate technique, rate constants have been determined for the gas phase reactions of Cl atoms with a series of organics at 296 ± 2 K and atmospheric pressure of air. Using a rate constant of 1.97 × 10−10cm3molecule−1s−1for the reaction of Cl atoms withn‐butane, the following rate constants (in units of 10−11cm3molecule−1s−1) were obtained: ethane, 6.38 ± 0.18; propane, 13.4 ± 0.5; isobutane, 13.7 ± 0.2;n‐pentane, 25.2 ± 1.2; isopentane, 20.3 ± 0.8; neopentane, 11.0 ± 0.3;n‐hexane, 30.3 ± 0.6; cyclohexane, 31.1 ± 1.4; 2,3‐dimethylbutane, 20.7 ± 0.6;n‐heptane, 34.1 ± 1.2; acetylene, 6.28 ± 0.18; ethene, 10.6 ± 0.3; propene, 24.4 ± 0.8; benzene, 1.5 ± 0.9; and toluene, 5.89 ± 0.36. These data are compared and discusse

ISSN:0538-8066    

DOI:10.1002/kin.550170105

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal reaction between SF4, and CF3OF has been studied between 142°C and 185°C. The reaction was found to be homogeneous and the only products formed are equimolecular amounts of SF6and CF3O2CF3and smaller amounts of CF3OSF5. The reaction mechanism was not affected by the total pressure, the oxygen pressure, or by the buildup of products. The experimental data can be explained by the following mechanism:The rate constants can be expressed as\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{lr} k_1 = (4.58 \pm 0.30) \times 10^7 \,{\rm exp( - 18900} \pm {\rm 1000}\,{\rm cal/}RT)M^{ - 1} \,{\rm s}^{{\rm - 1}} \\ k_2 = (3.88 \pm 0.30) \times 10^9 \,{\rm exp( - 9800} \pm {\rm 1000}\,{\rm cal/}RT)M^{ - 1} \,{\rm s}^{{\rm - 1}} \end{array} $$\end{documen

ISSN:0538-8066    

DOI:10.1002/kin.550170106

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractAn eigenvalue–eigenvector analysis is used to extract meaningful kinetic information from linear sensitivity coefficients computed for several species of a reacting system at several time points. The main advantage of this method lies in its ability to reveal those parts of the mechanism which consist of strongly interacting reactions, and to indicate their importance within the mechanism. Results can be used to solve three general kinetic problems. Firstly, an objective condition for constructing a minimal reaction set is presented. Secondly, the uncovered dependencies among the parameters are shown to confirm or deny validity of quasi‐steady‐state assumptions under the considered experimental conditions. Thirdly, taking into account only sensitivities of observed species, the analysis is used to yield error estimates on unknown parameters determined from the experimental observations, and to suggest the parameters that should be kept fixed in the estimation procedure. To illustrate we chose the well‐known hydrogen–bromine reaction and the kinetics of formaldehyde oxidation in the prese

ISSN:0538-8066    

DOI:10.1002/kin.550170107

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractBy addition of the light hydrogen isotope muonium (Mu = μ+e−) the 1‐ethyl‐hexen‐1‐yl radicals CH2= CHCH2CH2CH2CHCH2Mu, CH2= CHOCH2CH2CHCH2Mu, and CH2= CHCH2CH2OCHCH2Mu are generated in liquids. Their Fourier transform muon spin rotation spectra show linewidths increasing with increasing temperature which are attributed to the ring closure reactions. Analysis yields the absolute rate constants and their Arrhenius parameters. Together with previously reported results on analogous cyclization and on related ring fission reactions they are discussed in terms of steric and electronic effects on the reaction pathways and compared with predictions of semiempirical ca

ISSN:0538-8066    

DOI:10.1002/kin.550170108

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of the homolytic substitution of several trialkyltin iodides by iodine atoms are presented. Rate constants have been determined at three different temperatures and the following activation parameters calculated:A,Ea, and ΔS°≠. The observation that the activation energy, ΔG≠, is related to the driving force of the ion‐pair formation, leads to the conclusion that the charge‐transfer model is a valid approach for substitution in the reaction between R3SnI compounds and io

ISSN:0538-8066    

DOI:10.1002/kin.550170109

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractDi‐tert‐butyl nitroxide (DTBN) decomposes in aqueous solutions producing 2‐methyl‐2‐nitroso propane (MNP) andtert‐butanol. The process is acid catalyzed, it is of second order in DTBN, and takes place with a rate constant of (1.0 ± 0.1) M−2s−1. The reaction is also catalyzed by the anionic surfactant sodium dodecyl sulfate and by Fe(II) and Fe(III) ions. The catalysis by Fe(III) involves a very fast reduction of Fe(III) ions with concomitant formation of 2‐methyl‐2‐nitroso propane. The reaction catalyzed by Fe(II) also produces 2‐methyl‐2‐nitroso propane with a formation rate given by:d[MNP]/dt= (0.25 ± 0.10) [Fe(II)] [DTBN]. This reaction

ISSN:0538-8066    

DOI:10.1002/kin.550170110

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractVinyl and isopropyl radicals were generated by the pyrolysis of azoisopropane in the presence of acrolein at 473–563 K. Reaction products were analyzed by gas chromatography. Rate constant ratiosk2/k1= 0.02 ± 0.01 andk4/k3= 0.01 ± 0.005 are suggested for the following reactions:The rate constant ratio of reactions (7) and (c) obeys the Arrhenius equation\documentclass{article}\pagestyle{empty}\begin{document}$$ k_7 /k_c^{1/2} = (1.02 \pm 0.7)10^7 \,{\rm exp[ - (28}{\rm .42} \pm {\rm 2}{\rm .97)kJ/}RT]\,{\rm dm}^{{\rm 3/2}} \,{\rm mol}^{{\rm - 1/2}} \,{\rm s}^{{\rm - 1/2}} $$\end{document}The Arrhenius equation was derived for (k8+

ISSN:0538-8066    

DOI:10.1002/kin.550170111

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY