This compilation contains critically evaluated kinetic data on elementary homogeneous gas phase for use in modelling processes. Data sheets are presented for some 196 Each data sheet sets out relevant data, rate coefficient measurements, an assessment of the reliability of the data, references, and recommended rate parameters. Tables summarizing the preferred rate data are also given. The considered are limited largely to those involved in the of and ethane in air but a few relevant to the chemistry of exhaust gases and to the of aromatic compounds are also included.

This compilation updates and expands a previous evaluation of kinetic data on elementary, homogeneous, gas phase reactions of neutral species involved in combustion systems [J. Phys. Chem. Ref. Data 21, 411 (1992)]. The work has been carried out under the auspices of the European Community Energy Research and Development Program. Data sheets are presented for some 78 reactions and two tables in which preferred rate parameters are presented for reactions of ethyl, i-propyl, t-butyl, and allyl radicals are given. Each data sheet sets our relevant thermodynamic data, experimental kinetic data, references, and recommended rate parameters with their error limits. A table summarizing the recommended rate data is also given. The new reactions fall into two categories: first, to expand the previous compilation relating largely to the combustion in air of methane, ethane and aromatic compounds; and second, provide data for some of the key radicals involved in the combustion of higher alkanes.

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The ratio of rate constants for exchange at the methylene and methyl positions of butanone, k&,,/k{,,, is shown to be near 1.69 in 1 : I acetic acid-acetate buffer; nearly twice the value (0.86) for deuterioxide catalysis at 54.8". Methods of obtaining rate constants for acetate catalysis from composite rates (acetate and deuterioxide), or from rates in buffered media, are shown to be adequate for estimating rate ratios.Detailed temperature dependence of the relative rate constants for either system is not yet available but the effects are known to be small. For butanone enolizations the isokinetic temperature is in the neighborhood of 35", when reaction is catalyzed by deuterioxide in aqueous media.Le rapport des constantes de vitesse de I'echange aux positions methylene et methyl de la butanone, k!,,/k!,,, est pres de 1.69 dans un tampon 1 : 1 acide acetique-acetate et pres de deux fois cette valeur (0.86) dans le cas de la catalyse par I'oxyde de deutkrium a 54.8". Les methodes permettant d'obtenir les constantes de vitesse pour la catalyse par acetate a partir de vitesses combinkes (acetate et oxyde de deuterium) ou de vitesses en milieu tamponne sont estimees adequates pour la determination des rapports de vitesse.La dependance de la temperature sur les constantes de vitesse relatives de ces systemes n'a pas kte approfondie, mais les effets sont reconnus comme &ant faibles. Dans le cas des enolisations de la butanone, la temperature isocinttique se situe aux environs de 35" lorsque la reaction est catalysee par I'oxyde de deuterium en milieu aqueux.[Traduit par le journal]Canadian Journal of Chemistry. 50,3239 (1972) Discussion and Results In order to compare the ratio of hydrogen isotope exchange rates in butanone with the ratio of bromoketones formed in comparable circumstances (I ) it was desirable to redetermine the former. There is some controversy (2) with regard to the magnitude of the reactivity ratios for exchange (k&?/k&,)Z and concerning the effect of changing the catalyzing base from hydroxide to acetate.We have made two more measurements of the relative rates of exchange in butanone at 54.8". The media for these studies were 1 : 1 acetic acid -acetate buffers in D,O and exchange was followed by n.m.r., with two different n.m.r. spectrometers. The results, We have previously published two estimates of the reactivity ratio for acetate alone. In unbuffered, aqueous acetate the following average observe0 ratios, kkZ/k&,, for exchange have been reported: 1.4 for 1 M acetate at 59.2" (5), 1.4 for 2.5-5.0 M acetate at 500 (6), and 1.05 for 0.5 M acetate at 300 (7). These ratios are composite values, however, because hydrolysis of acetate in unbuffered systems produces appreciable concentrations of HO-, which has a much larger catalytic coefficient (by a factor greater than lo5) than acetate. We used an extrapolation technique (5) to isolate the catalytic coefficients of acetate toward butanone and obtained the ratio (k&2/k&3)i'z'-= 2.16 + 0.36. This number was checked by using buffer solutions (8) ...