Technical note: Improved synthetic routes to cis- and trans-(2-methyloxirane-2,3-diyl)dimethanol ( cis- and trans- β-isoprene epoxydiol)

Frauenheim, Molly; Surratt, Jason D.; Zhang, Zhenfa; Gold, Avram

We report improved synthetic routes to the isomeric isoprene-derived inline-formulaβ-epoxydiols (inline-formulaβ-IEPOX) in high yield (57 %–69 %) from inexpensive, readily available starting compounds. The syntheses do not require the protection/deprotection steps or time-consuming purification of intermediates and can readily be scaled up to yield the target IEPOX isomers in gram quantities. Emissions of isoprene (2-methyl-1,3-butadiene, Cinline-formula5Hinline-formula8), primarily from deciduous vegetation, constitute the largest source of nonmethane atmospheric hydrocarbons. In the gas phase under low-nitric-oxide (NO) conditions, addition of the atmospheric hydroxyl radical (OH) followed by rapid addition of Oinline-formula2 yields isoprene-derived hydroxyperoxyl radicals. The major sink (inline-formula>90 %) for the peroxyl radicals is a sequential reaction with the hydroperoxyl radical (HOinline-formula2), OH, and Oinline-formula2, which is then followed by the elimination of OH to yield a inline-formula M11inlinescrollmathml normal 2 : normal 1 32pt10ptsvg-formulamathimg7012a1454ab3dcc6883ce885c1e8c4f0 acp-23-7859-2023-ie00001.svg32pt10ptacp-23-7859-2023-ie00001.png mixture of cis- and trans-(2-methyloxirane-2,3-diyl)dimethanol (cis- and trans-inline-formulaβ-IEPOX). The IEPOX isomers account for about 80 % of closed-shell hydroxyperoxyl products and are rapidly taken up into acidic aerosols to form secondary organic aerosol (SOA). IEPOX-derived SOA makes a significant mass contribution to fine particulate matter (PMinline-formula2.5), which is known to be a major factor in climate forcing as well as adversely affecting respiratory and cardiovascular systems of exposed populations. Prediction of ambient PMinline-formula2.5 composition and distribution, both in regional- and global-scale atmospheric chemistry models, crucially depends on the accuracy of identification and quantitation of uptake product formation. Accessibility of authentic cis- and trans-inline-formulaβ-IEPOX in high purity and in large quantity for laboratory studies underpins progress in developing models as well as identification and quantitation of PMinline-formula2.5 components.

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Frauenheim, Molly / Surratt, Jason D. / Zhang, Zhenfa / et al: Technical note: Improved synthetic routes to cis- and trans-(2-methyloxirane-2,3-diyl)dimethanol (cis- and trans-β-isoprene epoxydiol). 2023. Copernicus Publications.

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