Atmospheric oxidation of volatile organic compounds (VOCs) leads to the formation of organic peroxy radicals that in turn affect the levels of nitrogen oxides (NOx = NO + NO2) and hydroperoxy radicals (HO2) in the troposphere. In low NOx/high HOx environments, acetone is among the most abundant oxygenated VOC. Following oxidation of acetone to form acetonylperoxy, reactions with HO2 impact the HOx balance by removing HO2 and working as a HOX radical sink through the formation of hydroperoxides (ROOH) or the generation of hydroxyl radicals (OH): HO2 + CH3C(O)CH2O2 → CH3C(O)CH2OOH + O2 HO2 + CH3C(O)CH2O2 → CH3C(O)CH2O + OH + O2 Recent experimental and theoretical work suggests that the OH yield is substantial; however, experimental findings have been scarce and limited only to room temperature. HO2 is also known to form hydrogen bonds with water molecules, which can lead to perturbations in the rate coefficients and product yields. This work presents the first direct detection of the OH product and the first investigation of the effects of pressure, temperature, and water on the reaction between HO2 and acetonylperoxy using pulsed laser photolysis coupled with simultaneous ultraviolet (UV) absorption spectroscopy and frequency modulation infrared (IR) spectroscopy. The UV absorption measurements are used to monitor the peroxy radical concentrations while near-IR and mid-IR lasers are used to monitor HO2 and product OH, respectively. The effects of changes in pressure, temperature, and relative humidity on the rate constants and branching ratios for the product channels and the atmospheric implications of these results will be discussed.

Acetonylperoxy and hydroperoxy kinetics from the perspective of the product hydroxyl radical

2019 Fall National Meeting

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