Rate coefficients are reported for the gas-phase reaction of the hydroxyl radical (OH) with C 2 HCl 3 (k 1 ) over an extended temperature range at 740 ‫ע‬ 10 torr in a He bath gas. Rate measurements exhibited complex behavior with a slight negative temperature dependence at temperatures below 650 K and positive temperature dependence at higher temperatures (650-750 K). The three-parameter modified Arrhenius equation adequately describes all of the data and is given by (in units of cm 3 moleculeError limits are 2r values. The activation energy derived from an Arrhenius fit to the data below 650 K is in good agreement with previous studies (Ͻ0.6 kcal/mol deviation). Quantum Rice-Ramsperger-Kassel (QRRK) modeling results are in reasonable agreement with experimental results and indicate the reaction is chemically activated. Although adduct stabilization and chlorine elimination channels are pressure dependent, the overall reaction is pressure independent above 0.1 atm. At temperatures characteristic of postcombustion conditions (i.e., ϳ1000 K), Cl elimination is the dominant reaction. H abstraction was found to be significant only at very high temperatures. The lack of a measurable kinetic isotope effect for k 1 is consistent with the modeling results. Based on the new measurements reported here and with the assumption that Cl elimination accounts for the entire measured rate at ϳ750 K, the extrapolated product-specific rate constant is given by (in units of cm 3 moleculeError limits are 2r values. This Cl elimination rate constant at 1000-1500 K is a factor of 5-8 times larger than extrapolation of previous low-temperature measurements. At 2000 K, H abstraction is a factor of 2-3 times faster than Cl elimination.

. Can. J . Chem. 59, 2184Chem. 59, (1981.Reactions of phenoxyl, iminoxyl, nitroxyl, peroxyl, and alkoxyl radicals with VO(acac), in solution have been studied by kinetic esr spectroscopy. Rates of reaction are first-order with respect to each reactant and radical reactivity increases in the order galvinoxyli 2,4,6-tri-tert-butylphenoxyl< di(l-adamanty1)methylene-iminoxyl< tert-butylperoxyl. Rates of reaction are retarded by pyridine and accelerated by methanol and there is an isotope effect on the rate when the hydroxyl proton of C H 3 0 H is replaced by deuterium. Vanadium-5 I nmr spectroscopy has demonstrated that several vanadium(V) products are formed while conventional product studies have indicated that, in the case of phenoxyl and alkoxyl, the radical is reduced almost exclusively to the parent phenol and alcohol and that VO(acac), is eventually regenerated in substantial yields. The net reaction is, therefore, catalytic reduction of the radical. Variable temperature esr studies have shown that phenoxyl and iminoxyl radicals and VO(acac), exist in equilibrium with diamagnetic reaction products. Utilisant la spectroscopie de rpe cinktique, on a etudie les reactions des radicaux phenoxyle, iminoxyle, nitroxyle, peroxyle et alkoxyle avec le VO(acac), en solution. Les vitesses de reaction sont du premier ordre par rapport a chaque rkactifet la reactivite des radicaux augmente dans I'ordre suivant: galvinoxyle < tri-tert-butyl-2,4,6 phenoxyle < di(adamanty1-1) methylhe iminoxyle < tert-butylperoxyle. Les vitesses de reaction sont ralenties par la pyridine et accelCrees par le methanol et le remplacement du proton hydroxylique du C H 3 0 H par un deuterium provoque un effet isotopique cinttique. La spectroscopie de rmn du vanadium-51 a demontre qu'il se forme plusieurs produits du vanadium(V) tandis que des etudes conventionnelles des produits indiquent que, dans le cas du phenoxyle et de I'alkoxyle, le radical est presqu'exclusivement reduit en phenol apparente et en alcool alors que le compose VO(acac), est regenere avec des rendements qui sont eventuellement substantiels. La reaction globale est cependant une reduction catalytique du radical. Des etudes de rpe ti temperature variable rtvelent que les radicaux phenoxyle et iminoxyle et le VO(acac), existent en equilibre avec des produits de reaction diamagnetiques.[Traduit par le journal] Introduction to give a vanadium(V)-ROOH complex which is ~t is well known that oxidation of olefins, Sul-followed by nucleophilic attack at the "activated" phides, sulphoxides, and amines by alkyl hydro--0-0-bond of the hydroperoxide by the peroxides (ROOH) is catalyzed by vanadyl acetyl-nucleo~hile. acetonate, VO(acac), (1).Although these oxidations are heterolytic there is some evidence that free-radicals are produced by

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