UV absorption spectrum of the C2 Criegee intermediate CH3CHOO

Smith, Mica C.; Ting, Wei-Lun; Chang, Chun-Hung; Takahashi, Kaito; Boering, K. A.; Lin, Jim J.

doi:10.1063/1.4892582

Cited by 84 publications

(93 citation statements)

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“…Beames et al 25 reported the UV-depletion spectrum of jetcooled CH 3 CHOO, which appears to be slightly narrower and shifted 15 nm to shorter wavelength relative to CH 2 OO. Similar to CH 2 OO, the UV absorption spectrum of thermal CH 3 CHOO reported by Smith et al 30 is much broader than the UV-depletion spectrum reported by Beames et al 25 Unlike for CH 2 OO, the spectrum reported by Smith et al 30 shows a broad feature with nearly no structure and a maximal UV cross section of (1.27 ± 0.11) × 10 at 328 nm; no conformation was specified. Sheps et al 26 separated the spectra of conformers of thermal CH 3 CHOO according to their reactivity towards H 2 O and SO 2 .…”

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confidence: 47%

“…After the discovery of this source of CH 2 OO, many researchers utilized this scheme to produce CH 2 OO and reported ultraviolet (UV) depletion, 18 UV absorption, 19,20 infrared (IR) absorption, 21 microwave, 22,23 and submillimeter-wave 24 spectra. Spectra of slightly larger Criegee intermediates such as acetaldehyde oxide (CH 3 CHOO), 15,[25][26][27][28][29][30][31][32] acetone oxide [(CH 3 ) 2 COO], 16,33 and propionaldehyde oxide (C 2 H 5 CHOO) 10 are also reported. Figure 1 shows the structures of CH 2 OO, syn-CH 3 CHOO, and anti-CH 3 CHOO.…”

Section: Spectroscopy Of Criegee Intermediatesmentioning

confidence: 99%

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Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Lee

2015

The Journal of Chemical Physics

159

122

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The Criegee intermediates, carbonyl oxides proposed by Criegee in 1949 as key intermediates in the ozonolysis of alkenes, play important roles in many aspects of atmospheric chemistry. Because direct detection of these gaseous intermediates was unavailable until recently, previous understanding of their reactions, derived from indirect experimental evidence, had great uncertainties. Recent laboratory detection of the simplest Criegee intermediate CH2OO and some larger members, produced from ultraviolet irradiation of corresponding diiodoalkanes in O2, with various methods such as photoionization, ultraviolet absorption, infrared absorption, and microwave spectroscopy opens a new door to improved understanding of the roles of these Criegee intermediates. Their structures and spectral parameters have been characterized; their significant zwitterionic nature is hence confirmed. CH2OO, along with other products, has also been detected directly with microwave spectroscopy in gaseous ozonolysis reactions of ethene. The detailed kinetics of the source reaction, CH2I + O2, which is critical to laboratory studies of CH2OO, are now understood satisfactorily. The kinetic investigations using direct detection identified some important atmospheric reactions, including reactions with NO2, SO2, water dimer, carboxylic acids, and carbonyl compounds. Efforts toward the characterization of larger Criegee intermediates and the investigation of related reactions are in progress. Some reactions of CH3CHOO are found to depend on conformation. This perspective examines progress toward the direct spectral characterization of Criegee intermediates and investigations of the associated reaction kinetics, and indicates some unresolved problems and prospective challenges for this exciting field of research.

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mentioning

confidence: 47%

Section: Spectroscopy Of Criegee Intermediatesmentioning

confidence: 99%

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Lee

2015

The Journal of Chemical Physics

159

122

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“…The experimental setup has been described in detail elsewhere (22,32). In brief, (CH 3 ) 2 COO was generated from photolysis of a gaseous mixture consisting of (CH 3 ) 2 CI 2 , O 2 , and buffer gas (N 2 ) at 248 nm (KrF excimer laser) via the established preparation method: (CH 3 ) 2 CI 2 + hν → (CH 3 ) 2 CI + I; (CH 3 ) 2 CI +O 2 → (CH 3 ) 2 COO + I (2, 30).…”

Section: Methodsmentioning

confidence: 99%

“…Other possible species in the absorption cell are SO 3 and acetone, which absorb rather weakly in the studied wavelength region [the absorption cross-sections σ for the relevant species are σ(SO 3 ) < 1 × 10 −21 cm 2 , σ(acetone) < 5 × 10 −20 cm 2 , and σ ∼ 10 −17 cm 2 for a CI] (30,31). Following the established method of spectral analysis in similar systems (22,(31)(32)(33), the absorption band of (CH 3 ) 2 COO can be obtained from the difference between the spectra in Fig. 2 A and B and is shown in Fig.…”

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confidence: 99%

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

Huang

Chao

Lin

2015

Proc. Natl. Acad. Sci. U.S.A.

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228

276

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Criegee intermediates are thought to play a role in atmospheric chemistry, in particular, the oxidation of SO 2 , which produces SO 3 and subsequently H 2 SO 4 , an important constituent of aerosols and acid rain. However, the impact of such oxidation reactions is affected by the reactions of Criegee intermediates with water vapor, because of high water concentrations in the troposphere. In this work, the kinetics of the reactions of dimethyl substituted Criegee intermediate (CH 3 ) 2 COO with water vapor and with SO 2 were directly measured via UV absorption of (CH 3 ) 2 COO under near-atmospheric conditions. The results indicate that (i) the water reaction with (CH 3 ) 2 COO is not fast enough (k H2O < 1.5 × 10 −16 cm 3 s −1 ) to consume atmospheric (CH 3 ) 2 COO significantly and (ii) (CH 3 ) 2 COO reacts with SO 2 at a near-gas-kinetic-limit rate (k SO2 = 1.3 × 10 −10 cm 3 s −1 ). These observations imply a significant fraction of atmospheric (CH 3 ) 2 COO may survive under humid conditions and react with SO 2 , very different from the case of the simplest Criegee intermediate CH 2 OO, in which the reaction with water dimer predominates in the CH 2 OO decay under typical tropospheric conditions. In addition, a significant pressure dependence was observed for the reaction of (CH 3 ) 2 COO with SO 2 , suggesting the use of low pressure rate may underestimate the impact of this reaction. This work demonstrates that the reactivity of a Criegee intermediate toward water vapor strongly depends on its structure, which will influence the main decay pathways and steady-state concentrations for various Criegee intermediates in the atmosphere. Ozonolysis of unsaturated hydrocarbons produces highly reactive Criegee intermediates (CIs) (1), which may (i) decompose to radical species like OH radicals or (ii) react with a number of atmospheric species, for example, with SO 2 to form SO 3 and with NO 2 to form NO 3 (2, 3). The SO 2 oxidation by CIs has gained special attentions because the SO 3 product would be converted into H 2 SO 4 , an important constituent of aerosols and acid rain (4-8). For example, Mauldin et al. (4) (2) demonstrated an efficient method to prepare a CI in a laboratory by the reaction of iodoalkyl radical with O 2 (for example, CH 2 I + O 2 → CH 2 OO + I). This method can produce a CI of high enough concentration that allows direct detection. With photoionization mass spectrometry (PIMS) detection, Welz et al. (2) measured the rate coefficients of the simplest CI (CH 2 OO) reactions with SO 2 and NO 2 . Notably, these new rate coefficients, confirmed by a few later investigations (9-11), are orders of magnitude larger than those previously used (12, 13) in atmospheric models (e.g., MCM v3.3, available at mcm.leeds. ac.uk/MCM/browse.htt?species=CH2OO), suggesting a greater role of CIs in atmospheric chemistry. This result also indicates previous ozonolysis analyses may be affected by complicated and partly unknown side reactions and may contain errors in some of the reported rate coefficients.Typical...

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“…87,88 ClCHOO can exist as two conformers, which can be labelled syn and anti, following the notation established for CH3CHOO according to the OOCCl torsion angle. Single point EOM-CCSD/aug-cc-pVTZ calculations have been performed at the ground state geometry to explore the effect of the Cl atom on the low-lying electronically excited states of both conformers relative to those of CH2OO.…”

Section: Clchoo Absorption Spectrummentioning

confidence: 99%

UV photodissociation dynamics of CHI₂Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate

Kapnas

Toulson

Foreman

et al. 2017

Phys. Chem. Chem. Phys.

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Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes.The photodissociation dynamics have been investigated using DC slice imaging, probing ground state I and spin-orbit excited I* atoms with 2+1 REMPI and single-photon VUV ionization. Total translational energy distributions are bimodal for I atoms and unimodal for I*, with around 72% of the available energy partitioned in to the internal degrees of freedom of the CHICl radical product, independent of photolysis wavelength. A bond dissociation energy of D0 = 1.73±0.11 eV is inferred from the wavelength dependence of the translational energy release, which is slightly weaker than typical C-I bonds. Analysis of the photofragment angular distributions indicate dissociation is prompt and occurs primarily via transitions to states of A″ symmetry. Complementary high-level MRCI calculations, including spin-orbit coupling, have been performed to characterize the excited states and confirm that states of A″ symmetry with highly mixed singlet and triplet character are predominantly responsible for the absorption spectrum. Transient absorption spectroscopy has been used to measure the absorption spectrum of ClCHOO produced from the reaction of CHICl with O2 over the range 345-440 nm. The absorption spectrum, tentatively assigned to the syn conformer, is at shorter wavelengths relative to that of CH2OO and shows far weaker vibrational structure.3

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UV absorption spectrum of the C2 Criegee intermediate CH3CHOO

Cited by 84 publications

References 42 publications

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

UV photodissociation dynamics of CHI₂Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate

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UV absorption spectrum of the C2 Criegee intermediate CH3CHOO

Cited by 84 publications

References 42 publications

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO 2

UV photodissociation dynamics of CHI2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate

Contact Info

Product

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Kinetics of a Criegee intermediate that would survive high humidity and may oxidize atmospheric SO ₂

UV photodissociation dynamics of CHI₂Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate