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

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