β-hydroxynitrates (HN) are major first-generation products formed following the OH or NO<sub>3</sub> initiated oxidation of terpenes, and their production is known to contribute to SOA formation. While heterogeneous reactions with gas-phase radicals or direct photolysis can degrade HN, hydrolysis reactions of HN with condensed water have been observed. Laboratory bulk aqueous studies have focused almost exclusively on smaller water soluble HN, however, HN derived from larger monoterpenes have a limited water solubility, and hence the role of hydrolysis reactions in mixed organic-aqueous remains fairly unconstrained. Here we synthesized the major HN isomers expected from four of the most atmospherically abundant monoterpenes and studied their degradation in bulk single-phase mixed aqueous-organic media. Degradation rates were measured in real-time using 2D H-NMR for a range of solvents and acid contents to provide insight into the reaction mechanism. Our results are discussed in the context of the rates of product formation and loss of the carbocation intermediate, highlighting the roles of hydrolysis and non-hydrolytic reactions in the fate of condensed phase HN.

Condensed phase reactions of BVOC-derived hydroxynitrates in mixed aqueous/organic media

ACS Spring 2022

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