Reaction between CH 3C(O)OOH (peracetic acid) and OH in the gas phase: a combined experimental and theoretical study of the kinetics and mechanism

Berasategui, Matias; Amedro, Damien; Vereecken, Luc; Lelieveld, Jos; Crowley, John N.

Peracetic acid (CHinline-formula3C(O)OOH) is one of the most abundant organic peroxides in the atmosphere; yet the kinetics of its reaction with OH, believed to be the major sink, have only been studied once experimentally. In this work we combine a pulsed-laser photolysis kinetic study of the title reaction with theoretical calculations of the rate coefficient and mechanism. We demonstrate that the rate coefficient is orders of magnitude lower than previously determined, with an experimentally derived upper limit of inline-formula M4inlinescrollmathml normal 4 × normal 10 - normal 14 46pt14ptsvg-formulamathimg347f9a23726b635d085f1782f83bec14 acp-20-13541-2020-ie00001.svg46pt14ptacp-20-13541-2020-ie00001.png  cminline-formula3 molec.inline-formula−1 sinline-formula−1. The relatively low rate coefficient is in good agreement with the theoretical result of inline-formula M8inlinescrollmathml normal 3 × normal 10 - normal 14 46pt14ptsvg-formulamathimg4d101635913758c61d7e0a25b12da9de acp-20-13541-2020-ie00002.svg46pt14ptacp-20-13541-2020-ie00002.png  cminline-formula3 molec.inline-formula−1 sinline-formula−1 at 298 K, increasing to inline-formula M12inlinescrollmathml normal 6 × normal 10 - normal 14 56pt14ptsvg-formulamathimg7864ece29747aa541b4917089a12eb66 acp-20-13541-2020-ie00003.svg56pt14ptacp-20-13541-2020-ie00003.png  cminline-formula3 molec.inline-formula−1 sinline-formula−1 in the cold upper troposphere but with associated uncertainty of a factor of 2. The reaction proceeds mainly via abstraction of the peroxidic hydrogen via a relatively weakly bonded and short-lived prereaction complex, in which H abstraction occurs only slowly due to a high barrier and low tunnelling probabilities. Our results imply that the lifetime of CHinline-formula3C(O)OOH with respect to OH-initiated degradation in the atmosphere is of the order of 1 year (not days as previously believed) and that its major sink in the free and upper troposphere is likely to be photolysis, with deposition important in the boundary layer.

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Berasategui, Matias / Amedro, Damien / Vereecken, Luc / et al: Reaction between CH3C(O)OOH (peracetic acid) and OH in the gas phase: a combined experimental and theoretical study of the kinetics and mechanism. 2020. Copernicus Publications.

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