摘要:

AbstractThe absolute rate constants for the reactions of NH2radicals with ethyl, isopropyl, andt‐butyl radicals have been measured at 298 K, using a flash photolysis–laser resonance absorption method. Radicals were generated by flashing ammonia in the presence of an olefin. A new measurement of the NH2extinction coefficient and oscillator strength at 597.73 nm was performed. The decay curves were simulated by adjusting the rate constants of both the reaction of NH2with the alkyl radical and the mutual interactions of alkyl radicals. The results arek(NH2+ alkyl) = 2.5 (±0.5), 2.0 (±0.4), and 2.5 (±0.5) × 1010M−1·s−1for ethyl, isopropyl, andt‐butyl radicals, respectively. The best simulations were obtained when takingk(alkyl + alkyl) = 1.2, 0.6, and 0.65 × 1010M−1·s−1for ethyl, isopropyl, andt‐butyl radicals, respectively, in good agreement

ISSN:0538-8066    

DOI:10.1002/kin.550140102

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractRate constants for the gas‐phase reactions of O3with ethene, propene, 1‐hexene, 1‐heptene, styrene,o‐,m‐, andp‐cresol,o‐ andm‐xylene, benzylchloride, acrylonitrile, and trichloroethene have been determined at 296 ± 2 K. The rate constants ranged from<5 × 10−21cm3molecule−1s−1form‐xylene to 2.16 × 10−17cm3molecule−1s−1for styrene, with those for ethene, propene, and 1‐hexene being in excell

ISSN:0538-8066    

DOI:10.1002/kin.550140103

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractMultistep hydrogen isotope exchange reactions, such as the íonization of a carbon acid via a carbanion intermediate in a protic solvent, when conducted using an isotopic tracer to monitor the exchange, have the unusual feature that their rate‐determining steps always refer to the transfer of the tracer isotope and never to the isotope present in macroscopic amounts. This property of these reactions is discussed and rationalized using a free energy versus reaction coordinate diagram. It is further shown that this property does not invalidate a commonly used method of measuring kinetic isotope effects on carbon acid ionization in which rates of incorporation of tritium tracers into RH and RD substrates are compared, despite the fact that tritium transfer is rate determining in both exchanges, but it is valid only if initial rate measurements are used. When the comparison is made in a protio solvent, e.g., H2O, the portion of the initial reaction which may be used depends strongly on the magnitude of the isotope effect. It ranges from less than 1% tritium incorporation for large isotope effects to 10% or more for isotope effects near unity. On the other hand, when a deuterated solvent, e.g., D2O, is used, the range of validity of the method for large isotope effects is extended dramatical

ISSN:0538-8066    

DOI:10.1002/kin.550140104

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe flash photolysis of biacetyl produces CO, C2H6, and CH3COCH3as main products, and in small amounts CO2, C2H4, and CH3CHO. The rate constants of reactions (2) and (3)\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {(1)} {2{\rm CH}_3 \to {\rm C}_2 } \\ \end{array}{\rm H}_6 $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {(2)} {{\rm CH}_3 + {\rm CH}_3 {\rm CO} \to {\rm CH}_3 {\rm COCH}_3 } \\ \end{array} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {(3)} {2{\rm CH}_3 {\rm CO} \to {\rm CH}_3 {\rm COCOCH}_3 } \\ \end{array} $$\end{document}of thermally equilibrated radicals were calculated from the amounts of products:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} k_2 = (2.98 \pm 0.17){\rm 10}^{{\rm 10}} {\rm dm}^{\rm 3} /{\rm mol} \cdot {\rm s} \\ k_3 = (2.43 \pm 0.14){\rm 10}^{{\rm 10}} {\rm dm}^{\rm 3} /{\rm mol} \cdot {\rm s} \\ \end{array} $$\end{document}.

ISSN:0538-8066    

DOI:10.1002/kin.550140105

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe thermal isomerization ofcis,anti,cis‐tricyclo[3.1.0.02,4] hexane was used to produce highly vibrationally excited 1,4‐cyclohexadiene. The competition between unimolecular decomposition of the energized diene (to benzene and hydrogen) and collisional stabilization was studied using the parent compound, SF6, CO2, N2, and He as quenching gases. Quenching efficiencies decreased in the order given above. By applying RRKM theory to the isomerization and decomposition reactions, it was possible to calculate the step size in a stepladder model of the deactivation of cyclohexadiene. The step sizes 〈ΔE〉 deduced (at 528 K and in units of kJ/mol) were: parent compound and SF6, 7; CO2, 5; N2, 4; He, 2. The study confirmed the utility of this unimolecular chemical activation system for energy transfer

ISSN:0538-8066    

DOI:10.1002/kin.550140106

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractMesityl 2,6‐xylyl ketone in 89.8% (w/w) sulfuric acid undergoes cleavage to give mesitylenesulfonic acid, xylenesulfonic acid, and carbon dioxide as final products. The reaction has been analyzed in terms of a series of first‐order reactions. Of the two possible reaction paths available it was shown that fission at the mesityl group is responsible for about 98.5% of the overall initial reaction at 2

ISSN:0538-8066    

DOI:10.1002/kin.550140107

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of deuterated ethyl chloride CH2DCH2Cl was studied in a static system in the pressure range of 0.1–26 torr, and the Arrhenius expression for the overall decomposition at the high‐pressure limit and in the temperature range of 670–1100 K was found to be\documentclass{article}\pagestyle{empty}\begin{document}$$ k_\infty = 10^{13.33 \pm 0.10} \exp [(- 57,200 \pm 500){\rm cal/mol/}RT]{\rm}s^{- 1} $$\end{document}The intramolecular isotopic effects were first examined in the pressure range of 0.1–26 torr at 837 K, and the branching ratiokH/kDwas found to decrease with increasing pressure. The RRKM‐theory calculations describe the experimental data well.The intramolecular isotopic effect was also examined in the temperature range of 728–926 K, and the branching ratio at the high pressure limit was given by the expression\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm H} /k_{\rm D} = (1.44 \pm 0.05)\exp [(1500 \pm 50){\rm cal/mol/}RT] $$\end{document}whenkHandkDare the rate constants for the HCl and DCl channels of elimination.The ArrheniusAfactors obtained at the high‐pressure limit together with the temperature‐dependent expression of the branching ratio provided additional experimental data for an assignment (fine‐tuned) of the vibrational frequencies of both activated complexes involved in the thermal decomposition of CH2DCH2Cl. The evaluated vibrational frequencies were then used in the RRKM calculations describing the pressure dependence of the intramolecular isotopic effect. The RRKM calculations and the experimental data were in good agreement, supporting the choice of vibrational frequencies for both the activated complexes as well as the trans

ISSN:0538-8066    

DOI:10.1002/kin.550140108

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe mechanisms for the conversion of molecular tritium gas to tritiated water are examined for tritium mixtures with (1) oxygen and nitrogen, (2) oxygen and argon, and (3) water and helium, for which previous experimental data exist. By analyzing results of these experiments in light of the radiation chemistry involved in a mixture of tritium and other gases, an understanding of the conversion mechanisms is reached. The formation of H and/or OH free radicals as intermediate species is of particular significance in the formation of HTO in that these radicals initiate a number of reactions which lead to the formation of water. These reactions are analyzed in terms of steady‐state kinetics to obtain predictive models which can be judged against the experimental observations. For the three experimentally observed mixtures, model agreement is found to be within a factor of 2

ISSN:0538-8066    

DOI:10.1002/kin.550140109

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550140101

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY