摘要:

AbstractTime‐resolved mass spectroscopy has been utilized to study the kinetics of methylradical association. The rate coefficient for the association process was determined by following the time dependence of ethane formation after flash photolysis of CH3I in the presence of N2. The net rate coefficient for the process 2CH3(+M) → C2H6(+M) has a high‐pressure limit of (4.0 ± 0.3) × 10−11cm3molecule−1sec−1at 313°K. This rate coefficient has found to be insensitive to the third‐body number densities for pressures ranging from 13 Torr down to below 0.5 Torr, indicating that the lifetime for dissociation of the intermediate C2H6* species is greater than 2 × 10−7sec at 313°K for a gas

ISSN:0538-8066    

DOI:10.1002/kin.550050502

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe previously published equation for the rate of a diffusion‐limited bimolecular reaction between chemically asymmetric molecules is studied numerically for the case that one of the reactant molecules is uniform. The results are reproduced quite well by a simple approximate chemical‐kinetic steady‐state scheme and, in principle, allow estimates of the size of the reactive region and of the activation‐controlled rate to be made from the observed dependence of rate on solvent viscosity. The simple scheme is easily generalized to the case of two nonuniform reactants. In general, restriction of reactivity to some fraction of the molecular surface (i.e., a steric factor) must reduce the observable reaction rate, but to an extent which is moderated by the rotational diffusion of the reactant mo

ISSN:0538-8066    

DOI:10.1002/kin.550050503

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe contribution of long‐range forces to the observed rates ofV→Venergy transfer processes has been studied. The theoretical model uses the first order perturbation approximation to generate a probability function, with the dipole–dipole perturbing potential as given by Margenau:Vif= [(1/6)1/2μ1 · μ2]R−3. The probability function derived is shown to be a strong function of the energy mismatch between the IR bands of the colliding molecules. The calculation emphasizes the importance of rotational state population effects, the most importantJstates being those which minimize the energy mismatch. A complete analysis of energy transfer between CO(v) and COS(000) wherev= 1,2, ⃛ 13 is presented. The calculation reveals the importance of combination bands in the energy transfer mechanism of polyatomics. The temperature dependence for near‐resonant processes is also studied and the importance of theV→Renergy transfer leads to the classification of ω0(band‐center energy mismatch) into three categories small, medium, and large, according to the temperature dependence that the corresponding processes exhibit. The predictions of the theoretical model are compared to experimental data

ISSN:0538-8066    

DOI:10.1002/kin.550050504

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractAn analysis is made of relationships to be expected between the enthalpies and entropies of reactions carried out in the gas and liquid phases, assuming ideal thermodynamic behavior of the components. The results of the analysis are compared with experimental results reported in the literature. Some discrepancies are noted. These may be the consequence of experimental error or may be due to substantial deviations from thermodynamic ideality. If the latter is commonplace, there will be difficulties in making useful predictions and correlations of thermodynamic and kinetic parameters in the liquid phase.

ISSN:0538-8066    

DOI:10.1002/kin.550050505

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe mechanism of isobutyraldehyde‐octene‐2 cooxidation at 20°C has been investigated. The ratio of cis to trans epoxides in the reaction products shows that, at aldehyde concentrations lower than 1.0M, the epoxide is formed mainly by a radical route. The difference in the ΔHof formation of cis and trans epoxides is around 0.8 kcal/mole at 20°. The isobutyraldehyde involved in the radical epoxidation chain has been found almost quantitatively to be isopropylhydroperoxide, which is formed through the decarboxylation of i‐PrCO2· radicals, addition of oxygen, and abstraction of hydrogen atoms from the aldehyde. A rate constant of about 14 M−1sec−1at 20° has been determined for the latter reaction. The chain length for the cooxdination reaction decreases from 75 to 20 as the isobutyraldehyde concentration goes from 1.0 to 0.3M. The termination step seems to involve mainly the interaction of two i‐PrO2· radicals. The cooxidation of octene‐2 with pivalaldehyde follows a similar mechanism, but the chain length is about ten times higher under the same expe

ISSN:0538-8066    

DOI:10.1002/kin.550050506

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractAzoethane was irradiated in the presence of carbon monoxide in the temperature range of 238 to 378 K. Kinetic parameters for the addition of ethyl radicals to carbon monoxide and for the decomposition of propionyl radicals were determined. The rate constants were found to be logk(cm3mol−1sec−1) = 11.19 ‐ 4.8/θ and logk(sec−1) = 12.77 ‐ 14.4/θ, respectively. Estimated thermochemical properties of the propionyl radical are ΔHf0= ‐10.6 ± 1.0 kcal mol−1,S0= 77.3 ± 1.0 cal K−1mol−1, andD(C2H5C

ISSN:0538-8066    

DOI:10.1002/kin.550050507

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractThe kinetics of the reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Fe}\left( {{\rm CO}} \right)_4 \left( {{\rm CH}_2{{=\!=}} {\rm CHX}} \right) + {\rm SbPh}_3 \to {\rm Fe}\left( {{\rm CO}} \right)_4 {\rm SbPh}_3 + {\rm CH}_2{{=\!=}}{\rm CHX}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \left( {{\rm X} = {\rm OEt},{\rm Ph},{\rm Bu}^n ,{\rm Cl},{\rm Br},{\rm CO}_2 {\rm Me},{\rm CN}} \right) $$\end{document}have been studied in toluene solution. The reaction occurs by a dissociative mechanism and the observation of an appreciable mass law retardation effect shows that Fe(CO)4is produced as an intermediate. Analysis of the effect of the substituent X on the stability of the complexes leads to the conclusion that π‐backbonding between the metal and the olefinic ligand is the major cause of the M‐olefin bond stre

ISSN:0538-8066    

DOI:10.1002/kin.550050508

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractTime‐resolved atomic absorption spectroscopy in the vacuum ultraviolet has been employed to monitor electronically excited oxygen atoms, O(21D2), following their genera‐tion by the flash photolysis of ozone in the Hartley band region. We report the first values for the absolute second‐order rate constants describing the removal of the excited atom on collision with the molecules H2, D2, CH4, NO, NO2, N2O, and C3O2. Where possible, these data are considered within the context of restrictions arising from spin and orbital symmetry and are further discussed in tems of previously reported relative rate data derived from indirect measurements. Consideration is given to the importance of these rate con‐stants in discussing processes taking place in the earth's atmosphere and in systems giving rise to chemical laser

ISSN:0538-8066    

DOI:10.1002/kin.550050509

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractFluorescence rise and decay processes were measured and rate parameters were determined for the pyrene‐tri‐n‐butylamine and pyrene‐N,N‐diethylaniline exciplex system in various solvents. An additional activation energy over that for the diffusional motion appears necessary for both exciplex formation and the deactivating quenching processes in the case of the pyrene‐tri‐n‐butylamine system. The rate‐determining step for these processes is electron transfer in the encounter collision leading to the nonrelaxed electr

ISSN:0538-8066    

DOI:10.1002/kin.550050510

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY

摘要:

AbstractRate parameters for the reaction of ground‐state atomic sulfur, S(3P), with the olefinscis‐2‐butene and tetramethylethylene have been determined over a temperature range of ∽280°K. A major finding of this study was that the rate constants for both reactions showed negative temperature dependencies. Whenkis expressed in the form of an Arrhenius equation, this necessarily leads to negative activation energies:k1= (4.68 ± 0.70) × 10−12exp(+0.23 ± 0.09 kcal/mole)/RT(219°‐500°K)k2= (4.68 ± 1.70) × 10−12exp(+1.29 ± 0.23 kcal/mole)/RT(252°‐500°K) Units are cm3molec−1s−1. When a threshold energy of 0.0 kcal/mole is assumed for reaction (2), the temperature dependence of the preexponential term has a value ofT−2. Making the usual simplifying assumptions, neither collision theory nor transition state theory leads to a preexponential factor with a strong enough negative temperature dependence. A comparison of these results with those derived from studies of the reactions of atomic oxygen, O(3P), with the same olefins shows that in both studies simple bimolecular processes were being examined. Also discussed are the possible experimental and theoretical ra

ISSN:0538-8066    

DOI:10.1002/kin.550050511

出版商:John Wiley&Sons, Inc.    

年代:1973

数据来源: WILEY