Kinetics and mechanism of the reactions of CH3CO and CH 3C(O)CH2 radicals with O2. Low-pressure discharge flow experiments and quantum chemical computations

Gergely Kovács, Judit Zádor, Edit Farkas, Rebeka Nádasdi, István Szilágyi, Sándor Dóbé, Tibor Bérces, Ferenc Márta, György Lendvay

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Abstract

The reactions CH3CO + O2 → products (1), CH 3CO + O2 → OH +other products (1b) and CH 3C(O)CH2 + O2 → products (2) have been studied in isothermal discharge flow reactors with laser induced fluorescence monitoring of OH and CH3C(O)CH2 radicals. The experiments have been performed at overall pressures between 1.33 and 10.91 mbar of helium and 298 ± 1 K reaction temperature. OH formation has been found to be the dominant reaction channel for CH3CO + O2: the branching ratio, Γ1b = k1b/k1, is close to unity at around 1 mbar, but decreases rapidly with increasing pressure. The rate constant of the overall reaction, k2, has been found to be pressure dependent: the fall-off behaviour has been analysed in comparison with reported data. Electronic structure calculations have confirmed that at room temperature the reaction of CH3C(O)CH2 with O2 is essentially a recombination-type process. At high temperatures, the further reactions of the acetonyl-peroxyl adduct may yield OH radicals, but the most probable channel seems to be the O2-catalysed keto-enol transformation of acetonyl. Implications of the results for atmospheric modelling studies have been discussed.

Original languageEnglish
Pages (from-to)4142-4154
Number of pages13
JournalPhysical Chemistry Chemical Physics
Volume9
Issue number31
DOIs
Publication statusPublished - Aug 13 2007

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ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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