Formic acid catalyzed isomerization and adduct formation of an isoprene-derived Criegee intermediate: experiment and theory

Autor:	Rebecca L. Caravan, Nisalak Trongsiriwat, Craig A. Taatjes, Stephen J. Klippenstein, Kendrew Au, Kristen Zuraski, Frank A. F. Winiberg, Shubhrangshu Pandit, Marsha I. Lester, David L. Osborn, Michael F. Vansco, Carl J. Percival, Trisha Bhagde, Patrick J. Walsh
Rok vydání:	2020
Předmět:	chemistry.chemical_classification Ozonolysis Double bond Formic acid General Physics and Astronomy Photochemistry Adduct chemistry.chemical_compound chemistry Criegee intermediate mental disorders Methyl vinyl ketone Physical and Theoretical Chemistry Isomerization Isoprene
Zdroj:	Physical Chemistry Chemical Physics. 22:26796-26805
ISSN:	1463-9084 1463-9076
Popis:	Isoprene is the most abundant non-methane hydrocarbon emitted into the Earth's atmosphere. Ozonolysis is an important atmospheric sink for isoprene, which generates reactive carbonyl oxide species (R1R2C[double bond, length as m-dash]O+O-) known as Criegee intermediates. This study focuses on characterizing the catalyzed isomerization and adduct formation pathways for the reaction between formic acid and methyl vinyl ketone oxide (MVK-oxide), a four-carbon unsaturated Criegee intermediate generated from isoprene ozonolysis. syn-MVK-oxide undergoes intramolecular 1,4 H-atom transfer to form a substituted vinyl hydroperoxide intermediate, 2-hydroperoxybuta-1,3-diene (HPBD), which subsequently decomposes to hydroxyl and vinoxylic radical products. Here, we report direct observation of HPBD generated by formic acid catalyzed isomerization of MVK-oxide under thermal conditions (298 K, 10 torr) using multiplexed photoionization mass spectrometry. The acid catalyzed isomerization of MVK-oxide proceeds by a double hydrogen-bonded interaction followed by a concerted H-atom transfer via submerged barriers to produce HPBD and regenerate formic acid. The analogous isomerization pathway catalyzed with deuterated formic acid (D2-formic acid) enables migration of a D atom to yield partially deuterated HPBD (DPBD), which is identified by its distinct mass (m/z 87) and photoionization threshold. In addition, bimolecular reaction of MVK-oxide with D2-formic acid forms a functionalized hydroperoxide adduct, which is the dominant product channel, and is compared to a previous bimolecular reaction study with normal formic acid. Complementary high-level theoretical calculations are performed to further investigate the reaction pathways and kinetics.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::81b1f3dae0d94a0753570ed33ad790b8 https://doi.org/10.1039/d0cp05018k Zobrazit plný text záznamu