摘要:

AbstractThe abstraction of hydrogen and deuterium from 1,2‐dichloroethane, 1,1,2‐trichloroethane, and two of their deuterated analogs by photochemically generated ground state chlorine atoms has been investigatedin the temperature range 0–95°C using methane as a competitor. Rate constants and their temperature coefficients are reported for the following reactionsOver the temperature range of this investigation an Arrhenius law temperature dependence was observed in all cases. Based on the adopted rate coefficient for the chlorination of methane [L.F. Keyser,J. Chem. Phys.,69, 214 (1978)]\documentclass{article}\pagestyle{empty}\begin{document}$$ k_r /{\rm cm}^{\rm 3} {\rm s}^{{\rm - 1}} = (1.65 \pm 0.32) \times 10^{ - 11} \exp [ - (1530 \pm 68)/T] $$\end{document}which is commensurate with the present temperature range, the following rate constant values (cm3s−1) are obtained:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = (4.93 \pm 0.96) \times 10^{ - 11} \exp [ - (1087 \pm 68)/T] $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_2 = (2.92 \pm 0.57) \times 10^{ - 11} \exp [ - (1362 \pm 68)/T] $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 = (2.39 \pm 0.57) \times 10^{ - 11} \exp [ - (1750 \pm 68)/T] $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_4 = (1.68 \pm 0.33) \times 10^{ - 11} \exp [ - (1965 \pm 68)/T] $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_5 = (1.22 \pm 0.24) \times 10^{ - 11} \exp [ - (1948 \pm 68)/T] $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ k_6 = (1.47 \pm 0.28) \times 10^{ - 11} \exp [ - (1910 \pm 68)/T] $$\end{document}The observed pure primary, and mixed primary plus α‐ and β3‐secondary kinetic isotope effects at 298 K arek3/k6= 2.73 ± 0.08, andk1/k2= 4.26 ± 0.12, respectively. Both show a normal temperature dependence decreasing tok3/k6= 2.39 ± 0.06 andk1/k2= 3.56 ± 0.09 at 370 K. Contrary to some simple theoretical expectations, the kinetic isotope effect for H/D abstraction decreases with increasing number of chlorine substituents in the geminal group in a parallel manner to the trend established previously for C1‐substitution in the adjacent group. The occurrence of a β‐secondary isotope effect,k4/k5, is established; this effect suggests a slight inverse

ISSN:0538-8066    

DOI:10.1002/kin.550180502

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractFollowing the kinetic investigation of the solvolysis of a range of cobalt(III) complexes in mixtures of water + cosolvent wherethe cosolvent enhances the solvent structure and decreases the dielectric constant, kinetic data are now reported for such a solvolysis in water + urea where urea acts as a structure breaker and enhances the dielectric constant. A plot of log (rate constant) against reciprocal of the dielectric constant shows that differential effects of changes in solvent structure occur between the initial and the transition states and, as in theinvestigations using structure‐enhancing cosolvents, the principal effect of change in solvent structure on the cobalt(III) cation occurs on the penta‐coordinated ion in the transition st

ISSN:0538-8066    

DOI:10.1002/kin.550180503

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe thermal reactions ofendo‐ andexo‐5‐Y bicyclo[2.2.2]oct‐2‐enes (NYBO and XYBO) whereY= methyl, ethyl, and isopropyl have been studied in the gas phase between 567 and 695 K. For both isomers they are parallel first‐order retro‐Diels‐Alder reactions with elimination of ethene (E) and monosubstituted ethene (YE).The observed Arrhenius parameters are used to discuss the mechanism and to estimate the heats of formation and the entropies of NYBO and XYBO. Group values are proposed for estimation of these thermochemical data for compounds of the same type by means of the me

ISSN:0538-8066    

DOI:10.1002/kin.550180504

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractRate constants have been measured for the reactions of four hydrocarbon radicals with O2in the gas phase at room temperature. Laserflash photolysis was used to generate low concentrations of radicals. A photoinization mass spectrometer followed the radical loss as a function of time. The measured pseudo first‐order decay rate of the radical and the absolute oxygen concentration were combined to give the absolute rate constants (in units of 10−12cm3molec−1s−1): isobutyl (2.9 ± 0.7); neopentyl (1.6 ± 0.3); cyclopentyl (17 ± 3); and cyclohexyl (14 ± 2). The cycloalkyl radicals have rate constants similar to those of other secondary radicals. However, the isobutyl and neopentyl radicals react more slowly than similar primary radicals. These new rate constants are compared in Figure 2 with the recently published correlation of reactive cross section with radical ionizatio

ISSN:0538-8066    

DOI:10.1002/kin.550180505

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractRate constants for overall H‐atom abstraction by hydroxyl radicals from CH and OH bonds are estimated for alkanes, haloalkanes, aldehydes, ketones, ethers, alcohols, nitriles, and nitrates over thetemperature range 250–1000 K. These estimated rate constants utilize the modified Arrhenius expression K = A'T2e−E'/Tin combination with the recommendations given in the recent review and evaluation of OH radical kinetics of Atkinson [1]. This estimation procedure gives good agreement, generally to within better than a factor of 2, of the estimated rate constants with theserecomm

ISSN:0538-8066    

DOI:10.1002/kin.550180506

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetics of the gas‐phase reactions of naphthalene, 2‐methylnaphthalene, and 2,3‐dimethylnaphthalene with O3and with OH radicals have been studied at 295 ± 1 K in one atmosphere of air. Upper limit rate constants for the O3reactions of<3 × 10−19,<4 × 10−19, and<4 × 10−19cm3molecule−1s−1were obtained for naphthalene, 2‐methylnaphthalene, and 2,3‐dimethylnaphthalene, respectively. For the OH radical reactions, rate constants of (in units of 10−11cm3molecule−1s−1) 2.59 ± 0.24, 5.23 ± 0.42, and 7.68 ± 0.48 were determined for naphthalene, 2±methylnaphthalene, and 2,3‐dimethylnaphthalene, respectively. These data show that under atmospheric conditions these naphthalenes will react mainly with the OH radical, with life‐times due to this reaction ranging from ca. 11 h for naphthalene t

ISSN:0538-8066    

DOI:10.1002/kin.550180507

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of propanoic acid dilute in argon has beenstudied in a single‐pulse shock tube over the temperature range of 1100‐1500 K and over the pressure range of 14‐18 atm. The decomposition kinetics have been satisfactorily computer modelled by means of afree radical mechanism involving H and OH chains.Recent single‐pulse shock tube product analyses of acetic acid decomposition have been computer modelled using a free radical mechanism for decarboxylation coupled to a unimolecular dehydration reaction.A comparison between the thermal decomposition kinetics of the C1C3alkanoic acids is made. The present studies do notprovide evidence for the participation of transition states involving a pentavalent carbon atom in the pyrolyses of the lower alkan

ISSN:0538-8066    

DOI:10.1002/kin.550180508

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe photooxidation of allyl chloride was studied by irradiation either in 100‐L Teflon bags or in a 22.7‐m3Teflon smog chamber in the presence of added NOx. In the absence of added hydrocarbons, the reaction involves a Cl atom chain, which leads to a highly reactive system. A reaction mechanism is presented to account for the following photooxidation products: chloroacetaldehyde, formaldehyde, 1,3‐dichloroacetone, 3‐chloroacrolein, acrolein, glyoxal, chloroperoxyacetyl nitrate, and peroxypropenyl nitrate. The rate constant for OH reaction with allyl chloride at 298 K was measured by a relative rate method under conditions where the Cl atom chain length was small and was found to be kOH= 1.7 × 10−11cm3molecule−1s−1. The rate constant for O3reaction with allylchloride at 298 K was found to be kO3= 1.5 × 10−1

ISSN:0538-8066    

DOI:10.1002/kin.550180509

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550180501

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY