Elucidating the Products and Kinetics of Bimolecular Alkene-Derived Peroxy Radical Reactions in the Lab and in the Field

Author: Murphy, Sara Edinger

Year: 2025

Degree: Dissertation (Ph.D.)

Advisor: Wennberg, Paul O.

Committee Members: Okumura, Mitchio; Seinfeld, John H.; Sander, Stanley P.; Wennberg, Paul O.

Option: Environmental Science and Engineering

DOI: 10.7907/q5bh-d327

Abstract

Although peroxy radicals, reactive compounds formed in the atmospheric oxidation of hydrocarbons, are primary drivers of atmospheric composition, several uncertainties remain with respect to their fates in both low and high NO environments. This thesis uses gas chromatography chemical ionization mass spectrometry (GC-CIMS) to identify and quantify the products of bimolecular peroxy radical reactions formed in both of these regimes in the lab and in the ambient environment. The first two chapters use laboratory experiments to probe the formation of a peroxide accretion product (ROOR) via peroxy radical self- and cross-reactions. In the first chapter, a method for studying the formation of the peroxide accretion product is developed and used to observe the formation of the accretion product of the ethene-derived hydroxy peroxy radical self-reaction. The self-reaction rate constant and the branching to the formation of the accretion product are measured, and the identity of the accretion product is confirmed by comparison to a synthesized standard. In the second chapter, the formation rate of the accretion product for a variety of small alkene-derived peroxy radical self-reactions is measured, and the observed relation- ship between peroxy radical structure and accretion product formation is discussed. Finally, the third chapter presents observations of organic nitrogen compounds formed via the reactions of biogenic and anthropogenic hydrocarbons in the Los Angeles urban atmosphere. The identities of several of these organic nitrates are confirmed by comparison to laboratory oxidation experiments, and the role these compounds play in the local nitrogen budget is discussed.

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