Laser Photolysis ‐ LIF Kinetic Studies of the Reactions of CH₃O and CH₂CHO with O₂ between 300 and 500 K

Abstract

Rate constants for the reactions (1) CH3O (methoxy) + O2 and (2) CH2CHO (vinoxy) + O2 have been determined between 300 and 500 K using a combined laser photolysis/laser induced fluorescence technique. Whereas reaction (1) is purely bimolecular with k1 = (5.5 ± 2.0) 10−14 exp(−1000 K/T) cm3s, reaction (2) appears to be a recombination process. For p = 130 mbar (M = He) we find k2 = (2.7 ± 1.5) 10−14 exp(668 K/T) cm3s, corresponding to a T−1.8 negative temperature dependence.

Atmospheric chemistry of alkanes

“…Furthermore, as discussed below in more detail, Batt and Robinson (1979) have obtained rate constants for the reaction of CH30 with 02 over the temperature range 380-430 K, relative to the rate constant for the reaction of CH30 with NQ (which in turn is directly related to the rate constant for the reaction of CH30 with NO). The rate constants so derived by Batt and Robinson (1979) are in good agreement with the more recent absolute data of Gutman et al (1982) and Lorenz et al (1985). Thus we use the general estimation technique of Batt (1979a) in our discussion below.…”

“…Zabarnick and Heicklen, 1985a), n-propoxy (Zabarnick and Heicklen, 1985b), isopropoxy (Batt, 1979b) and isobutoxy (Zabarnick and Heicklen, 1985c) radicals with 02, and measurements of the ratio of decomposition to reaction with 02 for the 2-butoxy radical, utilizing product yield studies in n-butane-NOx-air (Carter et al, 1979a)and n-butane-HONO-NOx-air (Cox et al, 1981) irradiations, are available. For the reaction of CH30 radicals with 02 the rate constants of Gutman et al (1982) and Lorenz et al (1985), though the temperature regimes studied (413-608 and 298-450 K, respectively) only overlap slightly, are in reasonable agreement. These two absolute studies define the rate constants for this reaction within reasonable error limits for temperatures between ""298 and 500 K. The recent Arrhenius repression of Lorenz et al (1985) of k(CH30 + 02) = 5.5 X 10 -14 e -1990/RT cm 3 molecule -1 sec -1 is used in this work since this study determined rate constants down to room temperature.…”

Reactions of alkoxy radicals under atmospheric conditions: The relative importance of decomposition versus reaction with O2

“…Absolute rate constants for the reactions of alkoxy radicals with 02 are available only for the methoxy (Gutman et al, 1982;Lorenz et al, 1985;Wantuck et al, 1987), ethoxy (Gutman et al, 1982;Hartmann et aL, 1990) and isopropoxy (Balla et al, 1985) radicals. For the other primary and secondary alkoxy radicals, the rate constants for H-atom abstraction by 02 have been assumed to depend only on whether the alkoxy radical is primary or secondary, regardless of the substituents Atkinson, 1990a), although earlier estimation methods did allow for the possibility of a dependence of the room temperature rate constant on the exothermicity of the reaction (Baldwin et al, 1977;Golden, 1979).…”

Elementary Reactions in the Methanol Oxidation System. Part I: Establishment of the Mechanism and Modelling of Laminar Burning Velocities

“…The temperature range below about 600 K was covered by two recent studies [75,76]. A pronounced non-Arrhenius behaviour occurs above 600 K which was attributed to high temperature channels yielding C H 2 0 + H + O2 and/or CHzOH + O2 in addition to the CHzO + H 0 2 low temperature channel (see Fig.…”