Impact of Molecular Structure on the OH-Initiated Oxidation Mechanism of 2-(2-Ethoxyethoxy)ethanol and Resulting Aerosol Formation

Reactive organic carbon (ROC) from volatile chemical products (VCPs) has emerged as an important precursor to urban ozone and secondary organic aerosol (SOA). Oxygenated ROC from VCPs may contribute to unexplained urban SOA; however, a predictive understanding is hampered by the structural complexity of multifunctional oxygenates. These functional groups may alter oxidation rates and open reaction pathways that are unavailable to hydrocarbons. We examine the OH-initiated oxidation of 2-(2-ethoxyethoxy)ethanol (2-2-EEE, C6H14O3), a potential contributor to urban SOA and a model compound for glycol diethers, which are commonly used as industrial solvents in paints, resins, and enamels. Our gas and particle-phase observations approach carbon closure (65(±14)%–107(±39)% of initial 2-2-EEE carbon accounted for at 15 h photochemical age) with stable reaction products that can be explained by a combination of peroxy radical (RO2) H-shifts, RO2 + HO2, and RO2 + NO reactions. Carbon-retaining (C6) products are consistent with hydroperoxy carbonyl species, including esters, and likely arise from a combination of RO2 H-shifts that are promoted by the diether structure, and RO2 + HO2 reactions. These products contribute to SOA and result in mass yields of 0.04–0.14. Rate coefficients from structure–activity relationships demonstrate that the diether structure drives rapid alkoxy radical (RO) decomposition and exerts important control over 2-2-EEE aerosol formation when RO2 + NO reactions are competitive. Functionalized C5-products dominate gas-phase carbon and likely arise from at least one RO2 H-shift, followed by RO decomposition. Our results highlight the importance of multiple oxygen-containing functional groups in controlling the reactive fate of 2-2-EEE, with relevance to other oxygenated VCP ROC emissions.