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Photochemical Smog
Published in Stanley Manahan, Environmental Chemistry, 2017
Isoprene reacts with ozone to produce initially Criegee intermediates. A Criegee intermediate (also called a Criegee zwitterion or Criegee biradical) is a carbonyl oxide with two charge centers:
Photochemical Smog
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Ozone adds across a double bond in isoprene to produce a reactive species called a Criegee intermediate. These species produce formaldehyde and hydroxyl radical, HO•, and are probably involved with the breakdown of sulfur dioxide and nitrogen dioxide in the atmosphere.5
Can (H2O) n (n = 1–2) as effective catalysts in the CH2OO + H2S reaction under tropospheric conditions?
Published in Molecular Physics, 2020
Rui Wang, Mingjie Wen, Xu Chen, Yongqi Zhang, Ximei Geng, Yingshi Su, Meng Liang, Xianzhao Shao, Wei Wang
As a highly reactive intermediate, the simplest Criegee intermediate, CH2OO, is known to play an important role in atmospheric oxidation chemistry and possibly in aerosol formation [1,2]. This intermediate can react quickly with SO2 with a rate coefficient of 4 × 10−11 cm3·molecule−1·s−1. Also, it can react with H2O, however, the rate of CH2OO + H2O reaction is significantly lower than that of CH2OO + SO2 reaction in the atmosphere [3–6]. H2S is not only a significant part of the atmospheric sulfur cycle [7,8], but also a factor in the formation of H2SO4, which contributes to aerosol nucleation and acid rain [9]. Since H2S only differs from H2O by the period of the central atom, the addition reaction of CH2OO + H2S has been widely studied in experimental [10] and theoretical [10,11] investigation.
Chemistry of hydroperoxycarbonyls in secondary organic aerosol
Published in Aerosol Science and Technology, 2018
Demetrios Pagonis, Paul J. Ziemann
The mechanism of formation of the AHPA model HOM from reaction of cyclodecene with O3 in the presence of 1-propanol is shown in Figure 2 (Ziemann 2003). The reaction is initiated by addition of O3 to the C = C double bond to form an unstable primary ozonide, which rapidly decomposes to an excited Criegee intermediate (ECI). In solution, essentially all ECI are thermalized by collisions with solvent to form stabilized Criegee intermediates (SCI), which react almost exclusively with 1-propanol to form the AHPA, 10-n-propoxy-10-hydroperoxydecanal (Zelikman et al. 1971). In the gas phase, the ECI can be thermalized by collisions with air to form SCI, which can undergo ring closure to form a secondary ozonide (SOZ) (Donahue et al. 2011), or in the presence of a high concentration of 1-propanol, the SCI can react to form the AHPA. Using the approach presented by Docherty et al. (2005), we estimate that the large excess of 1-propanol scavenges >95% of the stabilized Criegee intermediates and >99% of the OH radicals produced from the reaction. ECI also undergo isomerization and decomposition reactions that lead to stable products and the formation of RO2• radicals, which for the high VOC concentrations used here are expected to react with other RO2• radicals and HO2 radicals to form a variety of products containing carbonyl, hydroxyl, carboxyl, hydroperoxy, peroxycarboxyl (Ziemann 2002), and possibly ester (Müller et al. 2008) groups.
UV absorption spectrum and photodissociation dynamics of CH2OO following excitation to the B 1 A′ state
Published in Molecular Physics, 2021
Behnam Nikoobakht, Horst Köppel
Carbonyl oxides, also termed Criegee intermediates, are important reactive species that determine the outcome of many atmospheric processes, especially in the troposphere, under ambient conditions. Correspondingly, also their basic intramolecular properties have been widely studied in the past decade from an experimental [1–5] as well as theoretical [6–8] perspective. Pertinent reviews on various aspects exist [9–11]. In the following we confine ourselves to summarise those aspects most relevant to the present work, namely, focussing on excited electronic states of the smallest Criegee intermediate, CHOO.