摘要:

AbstractThe product quantum yields in the photolysis of 2,2,4,4‐tetramethyl‐3‐pentanone have been measured in homogeneous solvents of different viscosities, in micellar solutions of cetyltrimethylammonium chloride and sodium dodecyl sulfate, and in dioctadecyl ammonium chloride vesicles.The product quantum yield inn‐heptane was found to be 1. This value decreases to 0.5 in paraffin oil as a consequence of geminate recombination. In the presence of free radical scavengers, the extent of geminate disproportionation can be evaluated from the yields of isobutene and 2,2‐dimethyl propionaldehyde. From these yields and the geminate recombination yields the total amount of geminate processes and the disproportionation‐to‐combination ratio for caged radicals are estimated. It is found that micelles provide the most efficient cages. In these media only about 10% of the radicals avoid cage processes. The disproportionation‐to‐combination ratio of tert‐butyl and pivaloyl radicals was found to be extremely media dependent. The measured values ranged from about 0.2 in paraffin oil to 0.8 in cetyltrimethylammoniu

ISSN:0538-8066    

DOI:10.1002/kin.550160502

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe autooxidation of retinyl acetate and methyl retinoate was investigated in chlorobenzene at 45°C. The rates of thermal initiation in the retinyl acetate solutions were measured, and a value was determined of the rate constant for the reaction of oxygen with retinyl acetate (RH + O2→ R· + HO2·):kio= (1.3 ± 0.2) × 10−5L/mol · s. The number of moles of oxygen absorbed per mole of polyene depends on the substrate concentration. A kinetic scheme for the methyl retinoate autooxidation was proposed which takes into account the isomerization of primary peroxy radicals, and the rate constants for different elementary reactions were estimated. The partial rate constant for “allylic” hydrogen abstraction from retinyl acetate was estimated to be ≥ 1.65 × 103L/mol · s. A probable propagation sequence was proposed for the autooxidation o

ISSN:0538-8066    

DOI:10.1002/kin.550160503

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractKinetics of the thermal decomposition of acetic acid vapor dilute in argon have been studied over the temperature range of 1300–1950 K in a single‐pulse shock tube. The acid was found to decompose homogeneously and molecularly via two competing firstorder reaction channels at nearly equal rates, to form methane and carbon dioxide on the one hand, and ketene and water on the other. Fall‐off behavior has been taken into account and limiting high‐pressure rate constants for both channels have been derived. Ketene was found to decompose both unimolecularly to methylene radicals and carbon monoxide and also by a radical reaction with CH2to form ethylene and carbon monoxide. The rate constant derived for the unimolecular reaction was found to be in good agreement with an earlier shock tube measurement by H. G. Wagner and F. Zabel [Ber. Bunsenges Phys. Chem.,75, 114 (1971)]. The bimolecular reaction of ketene to produce allene and carbon dioxide, important in lower temperature reaction systems, has been found to be unimportant under the present conditions. A computer model for the decomposition kinetics involving 46 reactions of 21 species has been found to simulate the experimental yield data substantially. Sensitivity analyses have been used to identify reactions which make important contributions to the overall mechanism and yields of major products. Methylene radicals play important roles in determining yields of major

ISSN:0538-8066    

DOI:10.1002/kin.550160504

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reactions\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Cl}\,\, + \,\,{\rm RI} \to {\rm ICI}\,\, + \,\,{\rm R} $$\end{document}(R = CF3, C2F5, andi,‐C3F7) have been studied competitively in the gas phase over the range of 27–231°C. The following Arrhenius parameters were obtained:TextlogA,(cm3/mol · s)E,(kJ/mol)R = CF313.99 ± 0.2117.1 ± 2.0R = C2F513.97 ± 0.2011.5 ± 2.0R =i,‐C3F714.18 ± 0.2010.2 ± 2.0The above data lead to bond dissociation energiesD(R‐I) which are compared with previous published results. The following values are recommended:D,(CF3‐I) = 224,D,(C2F5‐I) = 219, andD,(i,

ISSN:0538-8066    

DOI:10.1002/kin.550160505

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe advantages and disadvantages of various methods of parametric sensitivity analysis in chemical kinetic modeling are discussed. Particular attention is given to estimates of computational labor for realistic problems, and quantitative comparisons are made utilizing a 52‐reaction, 11‐species CO oxidation mechanism. The authors′ CHEMSEN/AIM program compares favorably to other techniques in many circumstances, and provides the additional convenience of accepting input information in familiar chemical notation. This paper also reviews recent developments in theory of sensitivity analysis, relevant to chemical kinetic mod

ISSN:0538-8066    

DOI:10.1002/kin.550160506

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics of reactions involving halogen atom abstraction from haloalkanes by methyl radicals have been studied in the gas phase. Arrhenius parameters for halogen atom transfer were determined relative to those for methyl radical combination:TextRXlog10A2(L/mol · s)E2(kcal/mol)CFCl38.3 ± 0.210.7 ± 0.4CF3CCl37.9 ± 0.39.7 ± 0.6CF2Cl29.1 ± 0.411.3 ± 0.7CF3Cl8.8 ± 0.511.8 ± 1.0CF3CF2Cl8.3 ± 0.310.9 ± 0.7CF3Br8.6 ± 0.29.3 ± 0.5CF3I8.1 ± 0.14.3 ± 0.2CH3CH2I8.9 ± 0.37.4 ± 0.6The rate data obtained are used to provide information on the importance of polar effects for halogen abstr

ISSN:0538-8066    

DOI:10.1002/kin.550160507

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reactions of CCl3with O(3P) and O2and those of CCl3O2with NO have been studied at 295 K using discharge flow methods with helium as the bath gas. The rate coefficient for the reaction of CCl3with O was found to be (4.2 ± 0.6) × 10−11cm3/s and that for CCl3O2with NO was (18.6 ± 2.8) × 10−12cm3/s with both coefficients independent of [He]. For reaction between CCl3and O2the rate coefficient was found to increase from 1.51 7times; 10−14cm3/s to 7.88 × 10−14cm3/s as the [He] increased from 3.5 × 1016cm−3to 2.7 × 1017cm−3. There was no evidence for a direct two‐body reaction, and it is concluded that the only product of this reaction is CCl3O2. Examination of these results for CCl3+ O2in terms of current simplified falloff treatment suggests that the high‐pressure limit for this reaction is ∼ 2.5 × 10−12cm3/s, which may be compared with a direct measurement of the high‐pressure limit of 5 × 10−12cm3/s. A value of (5.8 ± 0.6) × 10−31cm6/s has been obtained fork0, the coefficient in the low‐pressure region. This value is compared with corresponding values found earlier for the (CH3, O2) and (CF3, O2) systems and with estim

ISSN:0538-8066    

DOI:10.1002/kin.550160508

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reaction of methyl radicals (Me) with hexafluoroacetone (HFA), generated from ditertiary butyl peroxide (dtBP), was studied over the temperature range of 402–433 K and the pressure range of 38–111 torr. The reaction resulted in the following displacement process taking place:where TFA refers to trifluoroacetone. The trifluoromethyl radicals that were generated abstract a hydrogen atom from the peroxide:such thatk6ais given by:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,\,k_{6{\rm a}} \left( {M^{ - 1} \cdot {\rm s}^{ - 1} } \right)\,\, = \,\,8.2\, \pm \,0.7\, - \,8.9\, \pm \,{{1.3} \mathord{\left/ {\vphantom {{1.3} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}where θ = 2.303RTkcal/mol. The interaction of methyl and trifluoromethyl radicals results in the following steps:Product analysis shows thatk17/k 151/2k 161/2= 2.0 ± 0.2 such thatk17= 1010.4±0.5M−1· s−1. The rate constantk5is given by:\documentclass{article}\pagestyle{empty}\begin{document}$$ {{{\rm log}\,\,k_5 } \mathord{\left/ {\vphantom {{{\rm log}\,\,k_5 } {\left( {M^{ - 1} \cdot {\rm s}^{ - 1} } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {M^{ - 1} \cdot {\rm s}^{ - 1} } \right)}}\,\, = \,\,8.0\, \pm \,1.3\, - \,5.1\, \pm \,{{0.7} \mathord{\left/ {\vphantom {{0.7} \theta }} \right. \kern-\nulldelimiterspace} \theta } $$\end{document}It is concluded that the preexponential factor for the addition of methyl radicals to ketones is lower than that for the addition of methyl radi

ISSN:0538-8066    

DOI:10.1002/kin.550160509

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550160501

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY