The falloff behavior of the CH3 + OH recombination reaction CH3 + OH -CH30H (la) has been quantitatively investigated for the first time. Methyl decay profiles were measured in a flow reactor at 300 K and in a pressure range between 0.3 and 6.2 mbar. The experimental conditions were such that a possible channel to 'CH, + H 2 0 did not contribute strongly to the CH3 profiles. Rate coefficients were extracted from the data by comparison of the experimental profiles with computer simulations. The results are in accord with the limiting rate coefficient suggested by Hochanadel et al., km1,(298 K) = 9.3 X 10-" cm3 molecule-' s-I.l The experimental falloff curve is described by use of this value for k", together with an interpolation formula given by Tree: from which an approximate value for the low-pressure limit kola = (2.5 1.0) X cm6 molecule-z s-l has been derived (bath gas helium). For a quantitative assessment of the possible channel to 'CHI + HzO, reaction Id, measurements of H20 were carried out, yielding an estimated upper limit for the rate coefficient of kId(300 K) 5 5 X cm3 molecule-' s-l.

No abstract

No abstract

The oxidation of propene has been studied at a total pressure of 60 Torrt between 400 and 520 "C, and a detailed product analysis made in the initial stages of reaction over a wide range of mixture composition. Mechanisms for the formation of the products are discussed. The initial rates of formation of hexa-1,Sdiene (HDE) and carbon monoxide are used to obtain A8 = 109.66*0.35 dm3 mol-' s-' and €8 = 78.6 4.5 kJ mol-', the former giving [allyl] from the known value of k ,

Results obtained from studies of t h e oxidation of propene between 400 and 520°C have been used to obtain the first Arrhenius parameters for t h e important chain initiation reaction RH + 0, --+ R + HO,, where RH is a hydrocarbon.A full product analysis in the early stages of reaction has been made for a number of mixtures at 400, 440, 480 and 520°C. It has been shown that hexa-1,5-diene is a major initial product and that its formation in reaction (8) represents the major termination process. By use of measurements of the initial rate of formation of hexa-1,5diene [(/?HDE)O]t so that secondary initiation is negligible, then in the absence of radical branching the simpleValues of k, at a constant temperature obtained from the relationship vary by less than a factor of two over a wide range of mixture composition, and the average values at each temperature give A , = lo9., dm3 mol-' s-' and E, = 162 kJ mol-'.