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Title:Infrared Spectra Of Gaseous (z)-3-iodo-but-2-en-1-yl [c2h3c(ch3)i] Radical, Methyl Vinyl Ketone Oxide [c2h3c(ch3)oo] Criegee Intermediate, And C2h3ci(ch3)oo
Author(s):Lee, Yuan-Pern
Contributor(s):Chung, Chen-An
Abstract:Methyl vinyl ketone oxide [MVKO, C$_{2}$H$_{3}$C(CH$_{3}$)OO], an important Criegee intermediate in ozonolysis of isoprene, was recently identified in laboratories with near infrared action spectrum (to produce OH) using photolysis of a gaseous mixture of 1,3-diiodo-but-2-ene [(CH$_{2}$I)HC=C(CH$_{3}$)I] and O$_{2}$,\footnote { V. P. ~Barber, S. ~Pandit, A. M. ~Green, N. ~Trongsiriwat, P. J. ~Walsh, S. J. ~Klippenstein, M. I. ~Lester, \textit{J. Am. Chem. Soc.} \underline{\textbf{140}}, 10866 (2018).} but its mid-infrared spectrum and the detailed mechanism of its formation remains unexplored. We employed a step-scan Fourier-transform infrared spectrometer to investigate the reaction intermediates. Upon irradiation at 248 nm of gaseous (Z)-1,3-diiodo-but-2-ene, the (Z)-3-iodo-but-2-en-1-yl [C$_{2}$H$_{3}$C(CH$_{3}$)I] radical was observed, indicating the fission of the terminal allylic C-I bond, not the central vinylic C-I bond. This radical is characterized by infrared absorption bands at 1406, 1261, 1109, 1019, 925, and 873 cm$^{-1}$. Upon irradiation at 248 nm of a gaseous mixture of (Z)-1,3-diiodo-but-2-ene and O$_{2}$ at 35 Torr, the Criegee intermediate MVKO, characterized by infrared absorption bands at 1416, 1383, 1346, 1060, 987, 948, and 908/916 cm$^{-1}$, was observed. At pressure 236 Torr, the reaction adduct 3-iodo-but-1-en-1-yl-peroxy [C$_{2}$H$_{3}$CI(CH$_{3}$)OO] radical, characterized by infrared absorption bands at 1375, 1213, 1108, 1063, 986, and 885 cm$^{-1}$, was observed. These new spectra of C$_{2}$H$_{3}$C(CH$_{3}$)I, C$_{2}$H$_{3}$C(CH$_{3}$)OO, and C$_{2}$H$_{3}$CI(CH$_{3}$)OO provide valuable information for the understanding of the formation mechanism of the Criegee intermediate MVKO from the source reaction of photolysis of (CH$_{2}$I)HC=C(CH$_{3}$)I in O$_{2}$ in laboratories. If time permits, we will discuss the formation kinetics and self-reaction of MVKO using a quantum-cascade laser.
Issue Date:2021-06-23
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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