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Peroxy Radical Isomerization of a Model Organic Compound Under Laboratory Chamber Conditions
MATTHEW GOSS, Victoria Barber, Yaowei Li, Alexander Zaytsev, Erik Helstrom, Francesca Majluf, Jordan Krechmer, Frank Keutsch, Jesse Kroll, MIT
Abstract Number: 140
Working Group: Aerosol Chemistry
Abstract
Peroxy radical isomerization is an important reaction contributing to the formation of highly oxidized molecules, which influence secondary organic aerosol (SOA) formation. While rates are highly dependent on structure, isomerization rates for some systems are fast enough to compete with bimolecular peroxy radical reactions. Previous studies of these reactions have used carefully selected reaction conditions, such as extremely slow photochemistry, to enable measurement of isomerization rates. However, these methods do not allow one to examine the impact of isomerization on SOA formation or product distribution across multiple generations of oxidation. In this study, we identify a model compound, 1,6-heptadiene, predicted to undergo isomerization as a primary reaction pathway with an estimated rate fast enough to compete with bimolecular reactions under typical chamber conditions. We perform chamber oxidation experiments under different reaction conditions and identify multi-generational products consistent with a hypothesized mechanism. Finally, we compare experimentally-derived isomerization rate constants to theoretically-based estimates, and examine the impacts of isomerization under different chamber conditions on aerosol chemical composition.