摘要:

AbstractThe pyrolyses of cyanomethylt‐butyl sulfide and its oxygen homologue have been studied in a stirred‐flow system over the temperature range 490–540°C and pressures between 5 and 14 Torr. In both cases, isobutene is formed as product in over 97% yield. Hydrogen sulfide is obtained in about half the amount of isobutene in the pyrolysis of the sulfide. Hydrogen cyanide is formed in the pyrolysis of the ether. The first‐order rate coefficients for the consumption of the reactants followed the Arrhenius equations Cyanomethylt‐butyl sulfide:\documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{12.63 \pm 0.23} \exp (- 201.7 \pm 3.5)\,{\rm kj}/{\rm mol }\,RT $$\end{document}Cyanomethylt‐butyl ether:\documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{11.27 \pm 0.30} \exp (- 186 \pm 5)\,{\rm kj}/{\rm mol }\,RT $$\end{document}A molecular mechanism involving polar four‐centered cyclic transition states is proposed for both reactions, with the CN group stabilizing the partial negative charge developed at the

ISSN:0538-8066    

DOI:10.1002/kin.550191202

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe kinetics of the Diels–Alder additions of CH2 CHCHO, CH2C(CH3)CHO, and CH2CHC(CH3)O to cyclohexa‐1,3‐diene (CHD) have been studied in the gas phase. The stereochemistry and the mechanism of these reactions are discussed. In contrast with other Diels–Alder additions involving CHD as diene, a biradical mechanism does not fit the experim

ISSN:0538-8066    

DOI:10.1002/kin.550191203

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe rate constants of the gas phase reaction of OH radicals with dimethyl sulfide (CH3SCH3) over the temperature range 260–393 K have been studied using the discharge flow‐resonance fluorescence technique. The rate constants were fitted by the Arrhenius equationk= (11.8 ± 2.2) × 10−12exp[−(236 ± 150)/T] cm3molecule−1s−1withk= (5.5 ± 1.0) × 10−12cm3molecule−1s−1at 298 K. Our results are in good agreement with the lower range of values reported previously. The observation of a small positive activation energy agrees well with that reported by Hynes et al. The rate constant was not affected by the total pressure variation (0.8–3.0 torr) or by the addition of oxygen (up to

ISSN:0538-8066    

DOI:10.1002/kin.550191204

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractWe present a kinetic study of the reaction of ground state silicon atoms with halogenated unsaturated organic compounds (R). Si(33PJ) was generated by the repetitive pulsed irradiation of SiCl4in the presence of excess helium buffer gas and the reactant R in a slow flow system, kinetically equivalent to a static system. The ground state atom was monitored by time‐resolved atomic resonance absorption spectroscopy at λ = 252 nm [Si(43PJ) ← Si(33PJ)] on time scales by which the optically metastable tates,Si(31D2) and Si(31S0) had relaxed to the3P state, using signal averaging methods. Computerized fitting of the resulting atomic decay traces in the presence of the various reactants, R, yielded the following new body of absolute second‐order rate constants (kR,T= 300 K, errors = 2sigma;):TextRkR/cm3molecule−1s−1C2F41.6 ± 0.2 × 10−10C2Cl49.9 ± 1.7 × 10−10CH2CF24.0 ± 0.6 × 10−10CHClCCl27.0 ± 1.1 × 10−10CF3CHCH24.6 ± 0.5 × 10−10C6H64.4 ± 1.0 times; 10−10C6F64.4 ± 0.6 × 10−10C6HF54.6 ± 1.3 × 10−10C6H2F43.9 ± 0.8 × 10−10C6F5—CF35.1 ± 0.6 × 10−10These data are compared, where appropriate, with analogous data for unsaturated hydrocarbon organic compounds. They are also discussed within the general

ISSN:0538-8066    

DOI:10.1002/kin.550191205

出版商:John Wiley&Sons, Inc.    

年代:1987

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 the cholorethenes and ethane at 298 ± 2 K and 735 torr total 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: vinyl chloride, 12.7 ± 0.2; 1,1‐dichloroethene, 14.0 ± 0.2;cis‐1,2‐dichloroethene, 9.65 ± 0.10;trans‐1,2‐dichloroethene, 9.58 ± 0.18; trichloroethene, 8.08 ± 0.10; tetrachloroethene, 4.13 ± 0.23; and ethane, 6.17 ± 0.08 (where the indicated error limits do not include the uncertainties in the rate constant forn‐butane). A small amount ofcis‐transisomerization was observed for the reactions involving thecis‐ andtrans‐1,2‐dichloroethenes. These data are compared and

ISSN:0538-8066    

DOI:10.1002/kin.550191206

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractBr atoms produced in a microwave discharge react abnormally rapidly with isobutane to produce HBr +t‐Butyl. A VLPR study of the system at high Br atom concentration (Br ˜ 1013/cc) between 298 and 363 K permits one to separate the effects of excited atoms, Br* (2P1/2) from ground state atoms, Br (2P3/2). Rate constants for the latter agree well with bromination measurements and permit fixing ΔH ƒ2980(tBu) at 9.5 ± 0.5kcal/mol in agreement with earli

ISSN:0538-8066    

DOI:10.1002/kin.550191207

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550191201

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY