University of Illinois Urbana-Champaign

Formation Reaction Mechanism And Infrared Spectra Of Criegee Intermediate Anti-trans-methacrolein Oxide [ch2c(ch3)choo] And Its Associated Precursor And Adduct Radicals

Lee, Yuan-Pern

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TN09_1.pptx
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https://hdl.handle.net/2142/116524

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Title
Formation Reaction Mechanism And Infrared Spectra Of Criegee Intermediate Anti-trans-methacrolein Oxide [ch2c(ch3)choo] And Its Associated Precursor And Adduct Radicals
Author(s)
Lee, Yuan-Pern
Contributor(s)
  • Chung, Chen-An
  • Su, Jung-Hsuan
  • Cai, Jia-Rong
Issue Date
2022-06-21
Keyword(s)
Radicals
Abstract
Methacrolein oxide (MACRO, CH$_{2}$C(CH$_{3}$)CHOO) is an important Criegee intermediate produced in ozonolysis of isoprene, the most abundantly-emitted non-methane hydrocarbon in the atmosphere. We employed a step-scan Fourier-transform infrared spectrometer to investigate the source reaction of MACRO in laboratories. Upon UV irradiation of precursor 1,3-diiodo-2-methyl-prop-1-ene CH$_{2}$IC(CH$_{3}$)CHI {\bf (1)}, the 3-iodo-2-methyl-prop-1-en-3-yl CH$_{2}$C(CH$_{3}$)CHI radical {\bf (2)} was detected, confirming the fission of the allylic C-I bond rather than the vinylic C-I bond. Upon UV irradiation of {\bf (1)} and O$_{2}$ near 21 Torr, {\it anti-trans}-MACRO {\bf (3a)} was observed to have an intense OO-stretching band near 917 \wn, much greater than those of {\it syn}-CH$_{3}$CHOO and (CH$_{3}$)$_{2}$COO, supporting a stronger O-O bond in MACRO because of resonance stabilization. At increased pressure (86-346 Torr), both reaction adducts CH$_{2}$C(CH$_{3}$)CHIOO {\bf (4)} and (CHI)C(CH$_{3}$)CH$_{2}$OO {\bf (5)} radicals were observed, indicating that O$_{2}$ can add to either carbon of the delocalized propenyl radical moiety of {\bf (2)}. We also employed a quantum-cascade laser and an UV laser to investigate the yield and kinetics of MACRO. The yield of MACRO is only ~5 \% from the source reaction, significantly smaller than other carbonyl oxides. The rate coefficients of the formation reaction and the self-reaction of MACRO will also be discussed.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
eng
Handle URL
https://hdl.handle.net/2142/116524
DOI
https://doi.org/10.15278/isms.2022.TN09
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Copyright 2022 held by the authors

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Abstracts & Presentations - 2022 International Symposium on Molecular Spectroscopy PRIMARY