A181-0002
Formic Acid Catalyzed Isomerization and Adduct Formation of an Isoprene-Derived Criegee Intermediate: Experiment and Theory
Tuesday, 15 December 2020
Poster
Michael F Vansco1, Rebecca Caravan2,3, Shubhrangshu Pandit4, Kristen Zuraski5,6, Frank Winiberg7, Kendrew Au2, Trisha Bhagde1, Nisalak Trongsiriwat1, Patrick J Walsh1, David L. Osborn2, Carl Percival5, S Klippenstein8, Craig Allen Taatjes9 and Marsha I Lester1, (1)University of Pennsylvania, Department of Chemistry, Philadelphia, PA, United States, (2)Sandia National Laboratories, Combustion Research Facility, Livermore, CA, United States, (3)Argonne National Laboratory, Chemical Sciences and Engineering Division, Argonne, IL, United States, (4)University of California San Diego, Department of Chemistry and Biochemistry, La Jolla, CA, United States, (5)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (6)NASA Postdoctoral Program Fellow, NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (7)California Institute of Technology, Pasadena, CA, United States, (8)Argonne National Laboratory, Chemical Sciences and Engineering Division, Lemont, IL, United States, (9)Sandia National Laboratories, Combustion Research Facility, Albuquerque, NM, United States
Abstract:
Isoprene is the most abundant non-methane hydrocarbon emitted into Earth’s atmosphere. Ozonolysis is an atmospheric sink for unsaturated hydrocarbons and generates reactive carbonyl oxide zwitterions (R
1R
2C=O
+O
−) known as Criegee intermediates (CIs). Isoprene ozonolysis leads to the formation of methyl vinyl ketone oxide (MVK-oxide), a four-carbon unsaturated CI. Recent work has demonstrated that the reaction of MVK-oxide with formic acid (FA) is a potentially significant sink for tropospheric FA. We present experimental and theoretical work that identifies and characterizes two reaction pathways in the reaction of MVK-oxide and FA. Direct experimental studies using multiplexed photoionization mass spectrometry (298 K, 10 Torr) demonstrate the formation of a highly oxygenated functionalized hydroperoxide product, resulting from the effectively barrierless insertion of MVK-oxide into formic acid. In addition, isotopically labeled experiments reveal a conformer-specific pathway where FA catalyzes the isomerization of
syn-MVK-oxide to a vinyl hydroperoxide (2-hydroperoxybuta-1,3-diene, HPBD). High-level theoretical calculations demonstrate that this FA catalyzed pathway proceeds by a double hydrogen-bonded interaction followed by a concerted H-atom transfer via submerged barriers to regenerate FA and yield HPBD. The rates, mechanisms and branching of these reaction pathways will be discussed.
This material is based upon work supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences (BES), US Department of Energy (USDOE) under contract to University of Pensylvania (DE-FG02-87ER13792) Argonne National Laboratory (DE-AC02-06CH11357) and Sandia National Laboratories). Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the USDOE’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the USDOE or the US Government. © 2020, California Institute of Technology.
