Assessing the Potential Mechanisms of Isomerization Reactions of Isoprene Epoxydiols on Secondary Organic Aerosol

Abstract

Laboratory and field measurements have demonstrated that isoprene epoxydiol (IEPDX) is the base component of a wide range of chemical species found in isoprene-derived secondary organic aerosol (SOA). To address newly raised questions concerning the chemical identities of IEPDX-derived SOA, the results of laboratory experiments carried out in bulk aqueous and organic media and analyzed via nuclear magnetic resonance spectroscopy and computed free energies of possible products are reported. The IEPDX nucleophilic addition product 2-methyltetrol was found to react too slowly in aqueous solution to explain the previous observation of tetrahydrofuran-based species. The IEPDX isomerization reactions in organic media were shown to mainly produce 3-methyltetrahydrofuran-2,4-diols, which were also established by the computational results as one of the most thermodynamically favorable possible IEPDX reaction products. However, these isomerization reactions were found to be relatively slow as compared to nucleophilic addition reactions, indicating that their occurrence on ambient SOA might be limited to low water content situations. No evidence was found for the production of the C-5 alkene triols or 3-methyltetrahydrofuran-3,4-diols previously reported for IEPDX reaction on SOA as analyzed via the gas chromatography/electron ionization-quadrupole mass spectrometry with prior trimethylsilyl derivatization method.

Publisher

American Chemical Society

Publication Date

8-7-2018

Publication Title

Environmental Science & Technology

Department

Chemistry and Biochemistry

Document Type

Article

DOI

10.1021/acs.est.8b01780

Keywords

2013 Southern Oxidant, Molecular composition, United States, Iepox-SOA, Volatility, Photooxidation, Atmosphere, Epoxides, Kinetics

Language

English

Format

text

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