Unimolecular Isomerizations and Oxygen Atom Loss in Formaldehyde and Acetaldehyde Carbonyl Oxides. A Theoretical Investigation

Anglada, Josep M.; Bofill, Josep María; Olivella, Santiago; Solé, Albert

doi:10.1021/ja953858a

Cited by 137 publications

(209 citation statements)

References 94 publications

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“…[ 13] The geometric parameters of the transition structure (TS4 in Figure 3) for the concerted POZ decomposition agree qualitatively with other theoretical results [14,75] except for the O1 ± O5 bond length, which is predicted by the CASSCF approach to be more than 0.3 longer. The computed activation energy at 0 K is 21.7 kcal mol À1 (18.7 kcal mol À1 taking into account the ZPVE corrections) is also comparable with other results from the literature [14] (Figure 2).…”

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confidence: 83%

The Ozonolysis of Ethylene: A Theoretical Study of the Gas-Phase Reaction Mechanism

1999

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The gas-phase reaction mechanism of ethylene ozonolysis has been investigated from a theoretical point of view. The formation of the ethylene primary ozonide (1,2,3-trioxolane, POZ) from the ozone ± ethylene reaction is calculated to be exothermic by 49.2 kcal mol À1 with an activation energy of 5.0 kcal mol À1 at 0 K, in agreement with experimental estimates. We have found two different paths for the cleavage of POZ, namely a concerted and a stepwise mechanism. The concerted path leads to the formation of Criegee intermediates (carbonyl oxide ± formaldehyde pairs), for which we have calculated an activation energy of 18.7 kcal mol À1 at 0 K. The non-concerted mechanism involves three different routes for the POZ decomposition, leading to the formation of Criegee intermediates with a computed activation energy of 21.6 kcal mol À1 at 0 K; to hydroperoxyacetaldehyde with a calculated activation energy of 22.8 kcal mol À1 at 0 K; and to oxirane excited molecular oxygen ( 1 D g ) with a higher activation energy. Moreover, hydroperoxyacetaldehyde is formed with an excess of energy, so that it can decompose yielding OH radicals. The reaction of carbonyl oxide and formaldehyde produces the ethylene secondary ozonide (1,2,4-trioxolane, SOZ) and involves the formation of a van der Waals complex on the reaction coordinate, prior to the transition state. The process is calculated to be exothermic by 46.0 kcal mol À1 and the energy of the transition state is computed to be lower than that of the reactants: this process can therefore be considered barrierless. SOZ cleaves by a stepwise mechanism and we have found two different fates for its decomposition: dioxymethane formaldehyde, and hydroxymethyl formate. The former is calculated to be endothermic by 33.3 kcal mol À1 with an energy barrier of 48.7 kcal mol À1, whereas the tautomerization of SOZ leading to hydroxymethyl formate is highly exothermic (72.2 kcal mol À1) and has an activation energy of 32.6 kcal mol À1 at 0 K. The unimolecular decomposition of dioxymethane, following three different paths, is also reported: dissociation into CO 2 H 2 , which is highly exothermic (111.6 kcal mol À1) and has a low energy barrier (3.0 kcal mol À1 ); isomerization to formic acid, also highly exothermic (101.9 kcal mol À1 ) with a low activation energy (2.2 kcal mol À1 at 0 K); and radical fragmentation into H HCOO, in a slightly endothermic process (4.9 kcal mol À1) with an activation energy of 18.4 kcal mol À1 at 0 K. The dissociation of formic acid into H 2 , CO 2 , CO and H 2 O and the decomposition of HCOO into H radicals CO 2 are also discussed.

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The Ozonolysis of Ethylene: A Theoretical Study of the Gas-Phase Reaction Mechanism

1999

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“…65,66 Anglada et al investigated with theory the ozonolysis of ethene 86 and the unimolecular isomerization and loss of an O-atom from CH 2 OO and CH 3 CHOO. 87 They concluded that energetic CH 2 OO can decompose to HCO + OH and O( 3 P) + H 2 CO or isomerize to dioxirane that isomerizes further to methylenebis(oxy). Methylenebis(oxy) decomposes to CO 2 + H 2 (or 2H) or isomerizes further to formic acid and decomposes to H 2 O + CO and CO 2 + H 2 .…”

Section: A Stabilization Vs Decompositionmentioning

confidence: 99%

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Lee

2015

The Journal of Chemical Physics

159

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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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“…Larger and more complex conformers such as heterosubstituted or cyclic structures are subject to additional unimolecular rearrangements (Vereecken and Francisco, 2012). On the unimolecular decomposition rates and products few experimental data are available (Horie et al, 1997(Horie et al, , 1999Fenske et al, 2000a;Novelli et al, 2014b;Kidwell et al, 2016;Fang et al, 2016a;, but more is available from theoretical studies explicitly focusing on the path followed by different conformers (Anglada et al, 1996;Aplincourt and Ruiz-López, 2000;Kroll et al, 2001;Zhang and Zhang, 2002;Nguyen et al, 2009b;Kuwata et al, 2010).…”

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Estimating the atmospheric concentration of Criegee intermediates and their possible interference in a FAGE-LIF instrument

et al. 2017

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Abstract. We analysed the extensive dataset from the HUMPPA-COPEC 2010 and the HOPE 2012 field campaigns in the boreal forest and rural environments of Finland and Germany, respectively, and estimated the abundance of stabilised Criegee intermediates (SCIs) in the lower troposphere. Based on laboratory tests, we propose that the background OH signal observed in our IPI-LIF-FAGE instrument during the aforementioned campaigns is caused at least partially by SCIs. This hypothesis is based on observed correlations with temperature and with concentrations of unsaturated volatile organic compounds and ozone. Just like SCIs, the background OH concentration can be removed through the addition of sulfur dioxide. SCIs also add to the previously underestimated production rate of sulfuric acid. An average estimate of the SCI concentration of ∼ 5.0 × 10 4 molecules cm −3 (with an order of magnitude uncertainty) is calculated for the two environments. This implies a very low ambient concentration of SCIs, though, over the boreal forest, significant for the conversion of SO 2 into H 2 SO 4 . The large uncertainties in these calculations, owing to the many unknowns in the chemistry of Criegee intermediates, emphasise the need to better understand these processes and their potential effect on the self-cleaning capacity of the atmosphere.

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Unimolecular Isomerizations and Oxygen Atom Loss in Formaldehyde and Acetaldehyde Carbonyl Oxides. A Theoretical Investigation

Cited by 137 publications

References 94 publications

The Ozonolysis of Ethylene: A Theoretical Study of the Gas-Phase Reaction Mechanism

The Ozonolysis of Ethylene: A Theoretical Study of the Gas-Phase Reaction Mechanism

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

Estimating the atmospheric concentration of Criegee intermediates and their possible interference in a FAGE-LIF instrument

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