Abstract
Abstract. In the atmosphere, one important class of reactions occurs in the aqueous phase in which organic compounds are known to undergo oxidation towards a number of radicals, among which OH radicals are the most reactive oxidants. In 2008, Monod and Doussin have proposed a new structure–activity relationship (SAR) to calculate OH-oxidation rate constants in the aqueous phase. This estimation method is based on the group-additivity principle and was until now limited to alkanes, alcohols, acids, bases and related polyfunctional compounds. In this work, the initial SAR is extended to carbonyl compounds, including aldehydes, ketones, dicarbonyls, hydroxy carbonyls, acidic carbonyls, their conjugated bases, and the hydrated form of all these compounds. To do so, only five descriptors have been added and none of the previously attributed descriptors were modified. This extension leads now to a SAR which is based on a database of 102 distinct compounds for which 252 experimental kinetic rate constants have been gathered and reviewed. The efficiency of this updated SAR is such that 58% of the rate constants could be calculated within ±20% of the experimental data and 76% within ±40% (respectively 41 and 72% for the carbonyl compounds alone).
Highlights
In the atmosphere, one important class of condensed phase chemical reactions occurs in the aqueous phase which can be found at various ionic strengths in deliquescent particles, activated particles or in the droplets of clouds, fog and rain
Aldehydes and ketones are major species directly emitted in the atmosphere, but the carbonyl function is systematically formed with high yields in the gas phase photooxidation processes of volatile organic compounds (VOCs) (Carlier et al, 1986, FinlaysonPitts and Pitts, 2000)
As can be seen, the additional SAR parameters lead to an efficient structure–activity relationship
Summary
One important class of condensed phase chemical reactions occurs in the aqueous phase which can be found at various ionic strengths in deliquescent particles, activated particles or in the droplets of clouds, fog and rain. In these media, organic compounds are known to undergo oxidation by a number of radicals, among which OH radicals are the most reactive oxidants (Herrmann et al, 2010). Aldehydes and ketones are major species directly emitted in the atmosphere, but the carbonyl function is systematically formed with high yields in the gas phase photooxidation processes of volatile organic compounds (VOCs) (Carlier et al, 1986, FinlaysonPitts and Pitts, 2000). It was recently evidenced that the heterogeneous and multiphase reactivity of polyfunctional carbonyl molecules (glyoxal, methylglyoxal, glycolaldehyde, pyruvic acid, methacrolein, methylvinylketone, etc.), could lead to important amounts of oligomers, representing a possible substantial source of humic like substances (HULIS) and/or
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