Atmospheric Fate of Methacrolein. 1. Peroxy Radical Isomerization Following Addition of OH and O2

Citation:

Crounse, JD, et al. “Atmospheric Fate of Methacrolein. 1. Peroxy Radical Isomerization Following Addition of OH and O2”. J. Phys. Chem. A 116 (2012): , 116, 5756–5762. Web.

Number:

24

ISSN:

1089-5639

Abstract:

Peroxy radicals formed by addition of {OH} and O2 to the olefinic carbon atoms in methacrolein react with {NO} to form methacrolein hydroxy nitrate and hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 $\pm$ 0.3 s?1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing hydroxyacetone and re-forming {OH.} Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition. Peroxy radicals formed by addition of {OH} and O2 to the olefinic carbon atoms in methacrolein react with {NO} to form methacrolein hydroxy nitrate and hydroxyacetone. We observe that the ratio of these two compounds, however, unexpectedly decreases as the lifetime of the peroxy radical increases. We propose that this results from an isomerization involving the 1,4-H-shift of the aldehydic hydrogen atom to the peroxy group. The inferred rate (0.5 $\pm$ 0.3 s?1 at T = 296 K) is consistent with estimates obtained from the potential energy surface determined by high level quantum calculations. The product, a hydroxy hydroperoxy carbonyl radical, decomposes rapidly, producing hydroxyacetone and re-forming {OH.} Simulations using a global chemical transport model suggest that most of the methacrolein hydroxy peroxy radicals formed in the atmosphere undergo isomerization and decomposition.

Publisher's Version

DOI:

10.1021/jp211560u
Last updated on 07/15/2015