摘要:

AbstractThe chemistry and energetics of the Criegee intermediate, a primary product of the ozonolysis of alkenes, are discussed in terms of recentab‐initiocalculations and laboratory studies. The experimental observations in O3–alkene systems can be rationalized on the basis of a general mechanism:where the ‡ represents the range of internal excitation energies available to the planar dioxymethylenes (i.e., the Criegee intermediates) initially formed via exothermic O3‐alkene reactions. Estimates are given for the rate constants of these reactions, and a critique is provided of the possible role of the Criegee intermediate and its isomers in the formation of alkanoic acid anhydrides in O3–alkene systems and in the formation of H2SO4aerosols in O3–alkene

ISSN:0538-8066    

DOI:10.1002/kin.550140302

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe gas‐phase kinetics and energetics of the Criegee intermediate, deduced from studies of O3‐alkene systems, suggest that a hydroxy‐substituted Criegee intermediate probably participates in the photooxidation of formaldehyde. In contradistinction, the existing evidence suggests that the Criegee intermediate and its isomers are probably not involved in alkyldioxy disproportionation reactions. In the case of O + oxoalkane addition reactions, the Criegee intermediate and its isomers are discussed in terms of a complex equilibr

ISSN:0538-8066    

DOI:10.1002/kin.550140303

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractA new mechanism is proposed for gas‐phase O3‐aldehyde reactions. Certain aspects of the new mechanism may be applicable also to O3‐aldehyde reactions in solution. The proposed mechanism involves initiation by addition of O3across the aldehydic CO bond. The initiation process and the subsequent chemistry together represent an exact analogue of the Criegee mechanism for O3‐alkene

ISSN:0538-8066    

DOI:10.1002/kin.550140304

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal reactions of bicyclo[4.2.2]deca‐3,7‐diene (BDD) and endo‐ and exo‐5‐vinylbicyclo[2.2.2]oct‐2‐ene (endo‐ and exo‐VBO) have been studied in the gas phase. The temperature range was 459–526 K for BDD, 476–563 K for endo‐VBO, and 513–578 K for exo‐VBO. The initial pressures were varied from 2 to about 40 torr. These compounds isomerize tocis‐1,2,4a,5,8,8a‐hexahydronaphtalene (HHN) and into each other, and decompose to 1,3‐butadiene (BD) + cyclohexa‐1,3‐diene (CHD). The reactions are homogeneous and first order. Their rate constants (in s−1) are given by:where the superscripts represent the reagents and the subscripts the products. The heats of formation and the entropies of e

ISSN:0538-8066    

DOI:10.1002/kin.550140305

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe thermal reactions of 1,3‐butadiene (BD) with cyclohexa‐1,3‐diene (CHD) have been studied in a static system between 437 and 526 K. The pressures of BD and CHD were varied from 61 to 397 torr and from 50 to 93 torr, respectively. The percentages of consumed BD and CHD were always kept lower than 14%. The reactions—in the order of importance—areAll the reactions are homogeneous and of the first order with respect to the reagents. Their rate constants (in L/mol·s) are given by\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \log _{10} k_{{\rm HHN}} = - (25,370 \pm 70)/4.576T + (7.02 \pm 0.03) \\ \log _{10} k_{{\rm KNDO}} = - (24,840 \pm 50)/4.576T + (6.58 \pm 0.02) \\ \log _{10} k_{{\rm BDD}} = - (25,530 \pm 50)/4.576T + (6.61 \pm 0.02) \\ \log _{10} k_{{\rm EXO}} = - (26,760 \pm 50)/4.576T + (7.06 \pm 0.02) \\ \end{array} $$\end{document}A thermochemical analysis of a biradical mechanism is in agreement with the

ISSN:0538-8066    

DOI:10.1002/kin.550140306

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe rate of adsorption of SO2on a prototype carbonaceous surface was measured at low pressure in a flow reactor. The measured rate indicates a maximum atmospheric loss of SO2by heterogeneous reaction of 1%/h for a particle density of 100 μg/m3. The capacity of carbon particles to adsorb SO2is limited at ∼1 mg SO2g−1C. NO2has no effect on the rate of SO2adsorption or the saturation beha

ISSN:0538-8066    

DOI:10.1002/kin.550140307

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe shock‐initiated decomposition of tetramethylgermane (1078–1242 K) has been found to involve successive elimination of methyl radicals with the rate constantk1for the first step given by\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_{\rm 1} {\rm}(s^{- 1}) = {\rm}(17.00 \pm 0.35) - (77.0 \pm 1.9)\theta {\rm kcal/mol} $$\end{document}In the presence of excess toluene the products were CH4(major), C2H4, and C2H6. Results relevant to the reaction of methyl radicals with toluene compared to methyl radical recombination are discus

ISSN:0538-8066    

DOI:10.1002/kin.550140308

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe gas‐phase kinetics of thermal decomposition of ethyl difluoroacetate, pentafluoropropionate, and hepatfluorobutyrate have been studied. The normal ester decomposition route to ethylene plus carboxylic acid is taken in each case, but the fluorinated acids decompose rapidly at the temperatures used. The primary decompositions are homogeneous and unimolecular, and the three Arrhenius equations are\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \log k{\rm}({\rm CF}_2 {\rm HCO}_2 {\rm Et}){\rm}({\rm s}^{- 1}) = (12.81 \pm 0.39) - (46,740 \pm 1290){\rm cal/mol/2}{\rm .303}RT \\ \log k{\rm}({\rm C}_2 {\rm F}_5 {\rm CO}_{\rm 2} {\rm Et}){\rm}({\rm s}^{- 1}) = (12.16 \pm 0.32) - (43,760 \pm 970){\rm cal/mol/2}{\rm .303}RT \\ \log k{\rm}({\rm C}_3 {\rm F}_7 {\rm CO}_{\rm 2} {\rm Et}){\rm}({\rm s}^{- 1}) = (12.29 \pm 0.13) - (43,880 \pm 370){\rm cal/mol/2}{\rm .303}RT \\ \end{array} $$\end{document}The postulate of a slightly electron‐rich γ carbon in six‐center ester transition states is supported by the higher rates and lowered activation energies observed when increasingly electron‐withdrawing fluorinated groups are linked to this center. The stabilization is reflected in a ρ constant of +0.30. The results are compared with previous work on α substitution in fluorina

ISSN:0538-8066    

DOI:10.1002/kin.550140309

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe disproportionation and combination reactions between CF2H and C2H5radicals have been studied in the gas phase from room temperature to 70°C. For the pathway which yields CF2H2+ C2H4, relative to CF2HC2H5, Δ = 0.072 ± 0.019. The competing reaction channel that produces CF2+ C2H6is approximately four times as efficient, with Δ = 0.265 ± 0.038. With CF2D radicals an isotope effect for the CF2+ C2H5D reaction pathway was observed with Δ

ISSN:0538-8066    

DOI:10.1002/kin.550140310

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550140311

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY