Abstract
Abstract. Isoprene epoxydiol (IEPOX) isomers are key gas-phase intermediates of isoprene atmospheric oxidation. Secondary organic aerosols derived from such intermediates have important impacts on air quality and health. We report here convergent and unambiguous pathways developed for the synthesis of isomeric IEPOX species and the rearrangement products cis- and trans-3-methyl-3,4-dihydroxytetrahydrofuran in good yield. The availability of such compounds is necessary to expedite research on isoprene atmospheric oxidation mechanisms and subsequent aerosol formation as well as the toxicological properties of the aerosols.
Highlights
Isoprene (2-methyl-1,3-butadiene, 1), the most abundant non-methane biogenic hydrocarbon emitted into the Earth’s atmosphere (Guenther et al, 2006), undergoes extensive atmospheric oxidation
All the nuclear magnetic resonance (NMR) spectra were recorded on a Varian INOVA 400 MHz spectrometer, with chemical shifts reported in ppm relative to tetramethylsilane
There are a number of methods for the preparation of 6, including catalytic epoxidation of isoprene (Sheng and Zajacek, 1970; Brill and Indictor, 1964; Indictor et al, 1965; Rasmussen et al, 1995), methylene addition to methacrolein (Welzel et al, 1987; Harwood et al, 1990), and a multi-step pathway starting from isoprene (Suzuki et al, 1986), these routes all suffer from poor yield and lack of convenience, limiting the overall yield for the preparation of isoprene yields four epoxydiol (IEPOX)-1
Summary
Isoprene (2-methyl-1,3-butadiene, 1), the most abundant non-methane biogenic hydrocarbon emitted into the Earth’s atmosphere (Guenther et al, 2006), undergoes extensive atmospheric oxidation. Under low nitric oxide (NO) conditions, gas-phase oxidation of isoprene yields four epoxydiol (IEPOX) isomers (Eddingsaas et al, 2010; Lin et al, 2012; Paulot et al, 2009; Surratt et al, 2010; Wang et al., 2005) (Fig. 1; IEPOX-1–4). The gas-phase formation of the IEPOX isomers in high yield can provide suitable precursors for SOA and elucidation of the reaction pathways involved in this chemistry will contribute to resolving an outstanding puzzle in atmospheric aerosol chemistry. Our published study (Lin et al, 2012) demonstrates that availability of authentic, pure and rigorously-characterized intermediates and standards is critical for investigations into the generation and subsequent reactions of the IEPOX isomers leading to SOA and the identification and quantitation of aerosol components.
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