Spectroscopy, kinetics, and dynamics of criegee intermediates

• Main Author: Lee, Yuan-Pern
• Other Authors: Asian Spectroscopy Conference 2020
• Format: Conference or Workshop Item
• Language: English
• Published: 2020
• Subjects: Science::Chemistry; Criegee Intermediates; Infrared Spectroscopy
• Online Access: https://hdl.handle.net/10356/144286
• Institution: Nanyang Technological University

Criegee intermediates, carbonyl oxides produced in ozonolysis of unsaturated hydrocarbons, play important roles in atmospheric chemistry. A new production scheme using photolysis of R2CI2 + O2 facilitated the production and direct detection of Criegee intermediates with various spectral techniques and has stimulated rapidly expanding research [1,2]. Methyl vinyl ketone oxide [MVKO, C2H3C(CH3)OO] is an important Criegee intermediates in ozonolysis of isoprene; it is resonance stabilized by its allyl moiety. We photolyzed a mixture of 1,3-diiodo-but-2-ene [(CH2I)HC=C(CH3)I] and O2 to produce MVKO and characterized the syn-trans- and syn-cis-conformers with transient infrared spectra recorded using a step-scan Fourier-transform spectrometer. The O‒O stretching band at 948 cm−1 is much greater than the corresponding bands of syn-CH3CHOO and (CH3)2COO Criegee intermediates at 871 and 887 cm−1, respectively, confirming a stronger O‒O bond due to resonance stabilization. We observed also iodoalkenyl radical C2H3C(CH3)I upon photolysis of the precursor to confirm the fission of the terminal allylic C‒I bond rather than the central vinylic C‒I bond of the precursor. At high pressure, the adduct C2H3C(CH3)IOO was also observed.