Direct kinetics study of CH2OO + methyl vinyl ketone and CH2OO + methacrolein reactions and an upper limit determination for CH2OO + CO reaction. Issue 29 (12th July 2018)

• Record Type: Journal Article
• Authors: Eskola, Arkke J.; Döntgen, Malte; Rotavera, Brandon; Caravan, Rebecca L.; Welz, Oliver; Savee, John D.; Osborn, David L.; Shallcross, Dudley E.; Percival, Carl J.; Taatjes, Craig A.
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 29(2018)
• Page Start: 19373
• Page End: 19381
• Publication Date: 2018-07-12
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp03606c
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Reactions of Criegee intermediate CH2 OO with unsaturated carbonyl compounds form secondary ozonide products. Abstract : Methyl vinyl ketone (MVK) and methacrolein (MACR) are important intermediate products in atmospheric degradation of volatile organic compounds, especially of isoprene. This work investigates the reactions of the smallest Criegee intermediate, CH2 OO, with its co-products from isoprene ozonolysis, MVK and MACR, using multiplexed photoionization mass spectrometry (MPIMS), with either tunable synchrotron radiation from the Advanced Light Source or Lyman-α (10.2 eV) radiation for photoionization. CH2 OO was produced via pulsed laser photolysis of CH2 I2 in the presence of excess O2 . Time-resolved measurements of reactant disappearance and of product formation were performed to monitor reaction progress; first order rate coefficients were obtained from exponential fits to the CH2 OO decays. The bimolecular reaction rate coefficients at 300 K and 4 Torr are k (CH2 OO + MVK) = (5.0 ± 0.4) × 10 −13 cm 3 s −1 and k (CH2 OO + MACR) = (4.4 ± 1.0) × 10 −13 cm 3 s −1, where the stated ±2 σ uncertainties are statistical uncertainties. Adduct formation is observed for both reactions and is attributed to the formation of a secondary ozonides (1, 2, 4-trioxolanes), supported by master equation calculations of the kinetics and the agreement between measured and calculated adiabatic ionization energies. Kinetics measurements were also performed for a possible bimolecular CH2 OO + CO reaction and for the reaction of CH2 OO with CF3 CHCH2 at 300 K and 4 Torr. For CH2 OO + CO, no reaction is observed and an upper limit is determined: k (CH2 OO + CO) < 2 × 10 −16 cm 3 s −1 . For CH2 OO + CF3 CHCH2, an upper limit of k (CH2 OO + CF3 CHCH2 ) < 2 × 10 −14 cm 3 s −1 is obtained.