Atmospheric oxidation of <i>α</i>,<i>β</i>-unsaturated ketones: kinetics and mechanism of the OH radical reaction

Abstract

Abstract. The OH-radical-initiated oxidation of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one was investigated in two atmospheric simulation chambers at 298±3 K and 990±15 mbar using long-path FTIR spectroscopy. The rate coefficients of the reactions of 3-methyl-3-penten-2-one and 4-methyl-3-penten-2-one with OH radicals were determined to be (6.5±1.2)×10-11 and (8.1±1.3)×10-11 cm3molecule-1s-1, respectively. To enlarge the kinetics data pool the rate coefficients of the target species with Cl atoms were determined to be (2.8±0.4)×10-10 and (3.1±0.4)×10-10 cm3molecule-1s-1, respectively. The mechanistic investigation of the OH-initiated oxidation focuses on the RO2+NO reaction. The quantified products were acetoin, acetaldehyde, biacetyl, CO2 and peroxyacetyl nitrate (PAN) for the reaction of 3-methyl-3-penten-2-one with OH radicals and acetone, methyl glyoxal, 2-hydroxy-2-methylpropanal, CO2 and peroxyacetyl nitrate (PAN) for the reaction of 4-methyl-3-penten-2-one with OH, respectively. Based on the calculated product yields an upper limit of 0.15 was determined for the yield of RONO2 derived from the OH reaction of 4-methyl-3-penten-2-one. By contrast, no RONO2 formation was observed for the OH reaction of 3-methyl-3-penten-2-one. Additionally, a simple model is presented to correct product yields for secondary processes.

Kinetics, Products, and Mechanisms Study of the Atmospheric Degradation of (E)-4-Methoxy-3-buten-2-one with Hydroxyl Radicals

“…Moreover, peroxyalkyl nitrates (ROONO 2 and R′OONO 2 ), alkyl nitrates (RONO 2 and R′ONO 2 ), and acetyl nitrates may also contribute to the final product distribution, depending on atmospheric conditions such as temperature and NO x concentration. Formation of alkyl nitrates has been observed in a similar reaction between OH radicals and 4-methyl-3-penten-2-one …”

“…The oxidation of 4M3B2O in the atmosphere may be initiated by a reaction with OH and nitrate (NO 3 ) radicals, Cl atoms in coastal and marine regions, and ozone molecules, and the reaction with OH radicals may be the main degradation pathway of 4M3B2O in the daytime. A large number of kinetic and product data are available for the reaction of OH with unsaturated ketones in terms of experiment and theory, − yet, literature data on the atmospheric chemistry of 4M3B2O is scarce, and only one experimental study was devoted to the gas-phase reaction of 4M3B2O with OH radicals. In 2020, Gibilisco et al investigated the kinetics of the reaction of 4M3B2O with OH radicals at 298 ± 3 K and 1 atm of synthetic air by using the relative-rate technique and Fourier transform infrared spectroscopy (FTIR).…”

Organic acid formation in the gas-phase ozonolysis of α,β-unsaturated ketones

“…The system is operated at an optical path length of 484.7 ± 0.8 m. The current set-up of the QUAREC chamber is described in greater details elsewhere. 23…”

“…Simulations of the temporal evolution of reaction products, possibly formed from peroxy radical reactions, were performed following the approach outlined previously. 23 A detailed description of the sensitivity analysis and model validation can be found elsewhere. 24 In contrast to previous applications, an explicit chemical mechanism was used for the relevant RO 2 reactions, in order to prove if the temporal behaviour of selected reaction products can be described by known reaction sequences.…”

Formation of a Resonance-Stabilized Radical Intermediate by Hydroxyl Radical Addition to Cyclopentadiene

“…Several experimental and theoretical studies have investigated the reaction of the OH radical with conjugated hydrocarbons. ,− For OH addition onto isoprene (H 2 CC­(CH 3 )–HCCH 2 ), the resonance-stabilized OH addition adduct has been shown to play a central role in the isoprene atmospheric oxidation mechanism. ,,, In the case of acrolein (H 2 CCH–HCO), the simplest conjugated carbonyl-containing molecule, addition of the OH radical onto one of the carbons of the vinyl group followed by O 2 addition leads to the formation of two different peroxy radicals . The location of the radical site after OH addition governs the O 2 addition mechanism and the structure of the final oxidation products.…”