摘要:

AbstractThermal curves obtained simultaneously at constant heating rates were used to study calcination of ZnCO3in air. Carroll and Manche's technique, Reich's equation, and Kissinger's method gave an average value for the activation energy of 23 kcal/mol. On the other hand, Coats and Redfern's technique showed the activation energy and preexponential factor to vary over wide ranges. They increase to a maximum and decrease again on increasing the temperature. Their values decrease as the heating rate was increased. One‐dimensional diffusion mechanism, obeying parabolic law, may control the entire calcination proces

ISSN:0538-8066    

DOI:10.1002/kin.550161202

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractRates and thermodynamic data have been obtained for the reversible self‐termination reaction:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm R}^ \cdot + {\rm R}^ \cdot \mathop{\buildrel\longleftarrow\over\longrightarrow}^{2k1}_{2k_{-1}}D $$\end{document}Involving aromatic 2‐(4′dimethylaminophenyl)indandione‐1,3‐yl (I), 2‐(4′diphenylaminophenyl)indandione‐1,3‐yl (II), and 2,6 di‐tert‐butyl‐4‐(β‐phthalylvinyl)‐phenoxyl (III) radicals in different solvents. The type of solvent does not tangibly affect the 2k1of Radical(I), obviously due to a compensation effect. The log(2k1) versus solvent parameterET(30) curves for the recombination of radicals (II) and (III) have been found to be V shaped, the minimum corresponding to chloroform. The intensive solvation of Radical (II) by chloroform converts the initially diffusion‐controlled recombination of the radical into an activated reaction. The log (2k−1) of the dimer of Radical (I) has been found to be a linear function of the Kirkwood parameter (ε ‐ 1)/(2ε + 1), the dissociation rate increasing with the dielectic constant of the solvent. The investigation revealed an isokinetic relationship for the decay of the dimer of Radical (I), an isokinetic temperature β = 408 K and isoequilibrium relationship for the reversible recombination of Radical (I) with β° = 651 K. For Radical (I) dimer decay In(2k−1) = const + 0.8 InK, whereKis the equilibrium constant of this reversible reaction. The transition state of Radical (I) dimer dissociation reaction looks more like a pair of radicals than the initial dimer. The role of specific solvation in radi

ISSN:0538-8066    

DOI:10.1002/kin.550161203

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe yield of benzene in the reaction of 1,4‐ and 1,3‐cyclohexadiene with OH radicals in the presence of oxygen was determined using H2O2and CH3ONO as OH radical sources. Both in the H2O2and the CH3ONO systems, the yield of benzene from 1,4‐cyclohexadiene was 15.3% and the yield from 1,3‐cyclohexadiene was 8.9%. On the basis of the obtained yields, the rate constant for allylic hydrogen abstraction per CH in cyclohexadiene was determined to be 3.8 × 10−12cm3molecule−1s−1. The branching ratio of the hydrogen abstraction to overall reaction for 1‐butene and 1‐pentene was estimated to be (25–14)% by applying the obtained rate constants. The result was in good agreement with the branching ratio determined directly by use of the discharge flow photoionization mass spectrometer by Biermann,

ISSN:0538-8066    

DOI:10.1002/kin.550161204

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination.The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.

ISSN:0538-8066    

DOI:10.1002/kin.550161205

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe recombination reaction O + O2→ O3was studied by laser flash photolysis of pure O2in the pressure range 3–20 atm, and of N2OO2mixtures in the bath gases Ar, N2, (CO2, and SF6) in the pressure range 3–200 atm. Fall‐off curves of the reaction have been derived. Low‐pressure rate coefficients were found to agree well with literature data. A high‐pressure rate coefficient ofk∞= (2.8 ± 1.0) × 10−12cm3molecule−1s−1was ob

ISSN:0538-8066    

DOI:10.1002/kin.550161206

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of SO2and of the primary dissociation product SO have been studied in shock waves by the uv absorption technique. The controversy about SO2dissociation data from uv absorption signals was resolved and attributed to the extensive overlap of SO2and SO uv absorption spectra. The derived rate coefficients arek1/[Ar] = 1015.6exp(‐420 kJmol−1/RT) cm3mol−1s−1(temperature range 3000–5000 K) for SO2dissociation, andk3/[Ar] = 1014.6exp(‐448 kJmol−1/RT) cm3mol−1s−1(temperature range 4000–6000 K) for SO dissociation. Anomalously high values of the apparent collision efficiencies βcin SO2dissociation are attributed to marked contributions from excit

ISSN:0538-8066    

DOI:10.1002/kin.550161207

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

Abstract5‐Methyl‐hexanone‐2, 3‐methyl‐pentanone‐2, and hexanone‐2 have been decomposed in comparative rate single pulse shock tube experiments. The mechanism of decomposition involves the breaking of carbon‐carbon bonds as well as molecular processes involving 6‐center complexes. The following rate expressions at 1100 K have been obtained:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} k(3{\rm - methyl - pentanone - 2} \to {\rm CH}_{\rm 3} {\rm \dot CO} + {\rm sC}_4 {\rm H}_9 .) = 10^{16.4} \exp (- 38,300/T)/{\rm s} \\ k(5{\rm - methyl - hexanone - 2} \to {\rm CH}_{\rm 3} {\rm \dot CO} + {\rm iC}_4 {\rm H}_9 .) = 10^{16.6} \exp (- 40,600/T)/{\rm s} \\ k(5{\rm - methyl - hexanone - 2} \to {\rm CH}_{\rm 3} {\rm COCH}_{\rm 3} + {\rm iC}_4 {\rm H}_8) = 10^{12.56} \exp (- 31,600/T)/{\rm s} \\ k({\rm hexanone - 2} \to {\rm CH}_{\rm 3} {\rm COCH}_{\rm 3} + {\rm C}_3 {\rm H}_6) = 10^{13.28} \exp (- 32,400/T)/{\rm s} \\ \end{array} $$\end{document}These results lead to ΔHf(CH3ĊO) = − 13.8 kJ and ΔHf(CH3COCH2·) = − 12.6 kJ at 300 K. They are compared with existing literature values and some generalizations are made with regard to the stabil

ISSN:0538-8066    

DOI:10.1002/kin.550161208

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe rate coefficient for the reaction of the hydroxyl radical, OH, with propane has been measured at 1220 K in shock tube experiments, and a value of (1.58 ± 0.24) × 1013cm3/mol s was obtained. This measured value is compared with previous experimental results and a transition‐state theory calculat

ISSN:0538-8066    

DOI:10.1002/kin.550161209

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractCalculations of low‐pressure limit, third‐order rate constants are presented for the association reactions A + O2+ N2and A + OH + N2(A = Li, Na, K) over the temperature range 200–2000 K and a comparison is made with the available experimental

ISSN:0538-8066    

DOI:10.1002/kin.550161210

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics of the unimolecular decomposition of phenyl acetate into phenol and ketene, reaction (1):\documentclass{article}\pagestyle{empty}\begin{document}$${\rm PhOCOCH}_3 \buildrel 1\over\rightarrow{\rm PhOH} + {\rm CH}_2 = {\rm C} = {\rm O}$$\end{document}has been studied under very low‐pressure conditions between 950 and 1120 K. In this range alternative processes such as the Fries rearrangement too‐hydroxyacetophenone or bond fission into phenoxyl and acetyl radicals are not observed. Based on present and previous evidence a novel four‐center transition state is proposed for reaction (1) which corresponds to the high‐pressure Arrhenius expression log (k1, s−1) = 12.8 – 56.2/θ, θ = 4.575 ×

ISSN:0538-8066    

DOI:10.1002/kin.550161211

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY