Ab initio study on the mechanism of the HCO+O2→HO2+CO reaction

Martı́nez-Ávila, Mónica; Peiró-Garcı́a, Julio; Ramírez‐Ramírez, Víctor M.; Nebot–Gil, Ignacio

doi:10.1016/s0009-2614(03)00106-4

Cited by 25 publications

(22 citation statements)

References 15 publications

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“…HC(O)O 2 was reported to be the intermediate product in the HCO þ O 2 reaction, and it can decompose rapidly to CO and HO 2 because of its instability (reactions 19). [59,60] In the present reaction system, we suggest that part of the HC(O)O 2 reacts with NO 2 to give HC(O)O 2 NO 2 (PFN) before its decomposition (reaction 22):…”

Section: Reaction Mechanisms Based On Observed Products Photolysis Mementioning

confidence: 89%

Photochemical reactions of methyl and ethyl nitrate: a dual role for alkyl nitrates in the nitrogen cycle

Chen

Zhang

2011

Environ. Chem.

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Environmental context. Alkyl nitrates are considered to be important intermediates in the atmospheric hydrocarbons-nitrogen oxides-ozone cycle, which significantly determines air quality and nitrogen exchange between the atmosphere and the Earth's surfaces. The present laboratory study investigates reaction products of alkyl nitrates to elucidate their photochemical reaction mechanisms in the atmosphere. The results provide a better understanding of the role played by alkyl nitrates in the atmospheric environment.Abstract. Alkyl nitrates (ANs) are important nitrogen-containing organic compounds and are usually considered to be temporary reservoirs of reactive nitrogen NO x (NO 2 and NO) in the atmosphere, although their atmospheric fates are incompletely understood. Here a laboratory study of the gas-phase photolysis and OH-initiated reactions of methyl nitrate (CH 3 ONO 2 ) and ethyl nitrate (C 2 H 5 ONO 2 ), as models of atmospheric ANs, is reported with a focus on elucidating the detailed photochemical reaction mechanisms of ANs in the atmosphere. A series of intermediate and end products were well characterised for the first time from the photochemical reactions of methyl and ethyl nitrate conducted under simulated atmospheric conditions. Notably, for both the photolysis and OH-initiated reactions of CH 3 ONO 2 and C 2 H 5 ONO 2 , unexpectedly high yields of HNO 3 (photochemically non-reactive nitrogen) were found and also unexpectedly high yields of peroxyacyl nitrates (RC(O)OONO 2 , where R ¼ H, CH 3 , CH 3 CH 2 ,y) (reactive nitrogen) have been found as CH 3 C(O)OONO 2 in the C 2 H 5 ONO 2 reaction or proposed as HC(O)OONO 2 in the CH 3 ONO 2 reaction. Although the yields of HNO 3 from the ANs under ambient conditions are likely variable and different from those obtained in the laboratory experiments reported here, the results imply that the ANs could potentially serve as a sink for reactive nitrogen in the atmosphere. The potential for this dual role of organic nitrates in the nitrogen cycle should be considered in the study of air quality and nitrogen exchange between the atmosphere and surface. Finally, an attempt was made to estimate the production of HNO 3 and peroxyacyl nitrates derived from NO x by ANs as intermediates in the atmosphere.

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Section: Reaction Mechanisms Based On Observed Products Photolysis Mementioning

confidence: 89%

Photochemical reactions of methyl and ethyl nitrate: a dual role for alkyl nitrates in the nitrogen cycle

Chen

Zhang

2011

Environ. Chem.

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“…In the presence of O 2 under our laboratory conditions, the newly formed radicals quickly react with O 2 in a barrierless, exothermic reaction that yields peroxy radicals. [27][28][29][30] The peroxy radicals undergo H-atom transfer to form QOOH intermediates, which decay via submerged barriers to form closed shell carbonyl species. [28][29][30] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 28 carbonyl products that are observed, the peroxy chemistry also results in OH or HO 2 radical co-products with pressure-dependent yields.…”

Section: Discussionmentioning

confidence: 99%

“…16 Under our low pressure experimental conditions (298 K, 10 torr), the radical products react with O 2 to form ROO, which undergoes further unimolecular decay via QOOH intermediates to yield stable carbonyl products that are detected and an OH or HO 2 radical co-product. [27][28][29][30] The radical products are expected to have a similar fate under atmospheric conditions (298 K, 760 torr) in pristine locations (low NO x concentrations). [64][65] Again, the radicals will react rapidly with O 2 to form ROO, which can undergo unimolecular decay to stable carbonyl products with an OH or HO 2 radical co-product.…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

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Experimental Evidence of Dioxole Unimolecular Decay Pathway for Isoprene-Derived Criegee Intermediates

et al. 2020

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Ozonolysis of isoprene, one of the most abundant volatile organic compounds emitted into the Earth's atmosphere, generates two four-carbon unsaturated Criegee intermediates, methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide). The extended conjugation between the vinyl substituent and carbonyl oxide groups of these Criegee intermediates facilitates rapid electrocyclic ring closures that form 5-membered cyclic peroxides, known as dioxoles. This study reports the first experimental evidence of this novel decay pathway, which is predicted to be the dominant atmospheric sink for specific conformational forms of MVK-oxide (anti) and MACR-oxide (syn) with the vinyl substituent adjacent to the terminal O atom. The resulting dioxoles are predicted to undergo rapid unimolecular decay to oxygenated hydrocarbon radical products, including acetyl, vinoxy, formyl, and 2methyl-vinoxy radicals. In the presence of O 2 , these radicals rapidly react to form peroxy radicals (ROO), which quickly decay via carbon-centered radical intermediates (QOOH) to stable carbonyl products that are identified in this work. The carbonyl products are detected under thermal conditions (298 K, 10 torr He) using multiplexed photoionization mass spectrometry (MPIMS). The main products (and associated relative abundances) originating from unimolecular decay of anti-MVK-oxide and subsequent reaction with O 2 are formaldehyde (88 ± 5%), ketene (9 ± 1%) and glyoxal (3 ± 1%). Those identified from the unimolecular decay of syn-MACR-oxide and subsequent reaction of O 2 are acetaldehyde (37 ± 7%), vinyl alcohol (9 ± 1%), methylketene (2 ± 1%), and acrolein (52 ± 5%). In addition to the stable carbonyl products, the secondary peroxy chemistry also generates OH or HO 2 radical co-products. distinctly different than simple saturated carbonyl oxides, such as formaldehyde oxide (CH 2 OO) and alkyl-substituted Criegee intermediates, which have four π electron systems (C=O + O -). [8][9][10][11][12][13][14][15][16] In addition, MVK-oxide and MACR-oxide each have four conformational forms with similar predicted ground state energies (within ca. 3 kcal mol -1 ). The four conformational forms are separated into two groups based on:(1) the orientation of the terminal oxygen with respect to the vinyl group (syn and anti), and (2) the orientation of the vinyl group with respect to the C=O group (cis and trans). Under thermal conditions (298 K), the cis and trans conformations will rapidly interconvert by rotation about the C-C bond (indicated by the curved arrow in Scheme 1). [15][16][17] The syn and anti configurations do not interconvert at ambient temperature due to high barriers for rotation about the C=O bond and are treated as distinct chemical species with different unimolecular and in some cases bimolecular reaction pathways. 15,[17][18][19] The product branching from isoprene ozonolysis has been investigated using master equation modeling, [18][19][20] yielding results that differ depending on the theoretical method used. The most recent c...

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“…To ascertain its expected reliability, we computed the T 1 diagnostic 83 values for all the species involved in the reactions that are used for benchmark study, since this diagnostic has been proposed as a measure of the suitability of singereference coupled cluster theory. The molecule with the largest T 1 diagnostic value is the transition state structure of reaction (R1) (Si 4 H 10 À ), for which the value is 0.0252 computed by CCSD(T)/aug-cc-pVTZ; this value is much smaller than 0.045, which has been suggested [84][85][86] as a criterion for the applicability of single-reference methods to open-shell molecules, and hence we concluded that CCSD(T) can serve as a reference for testing other methods in this work.…”

Section: Benchmark Of Various Density Functionalsmentioning

confidence: 96%

Silane-initiated nucleation in chemically active plasmas: validation of density functionals, mechanisms, and pressure-dependent variational transition state calculations

Bao

Truhlar

2016

Phys. Chem. Chem. Phys.

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The growth of anionic silicon hydride clusters is a critically important process in nanodusty plasmas. In the current study, we focus on the formation of homologs of silylene (Sin+1H2n+2(-), n = 3, 4) and silyl (SinH2n+1(-), n = 4, 5) anions via anion-neutral reaction pathways. Species like silyl or silylene anions and their related elementary reactions, which are involved in the formation of silicon hydride clusters, were not used in developing exchange-correlation (xc) density functionals (i.e., they were not included in the training set of semiempirical density functionals); therefore, we explored the accuracy of various widely used xc density functionals based on reaction energies and barrier heights. Among the 21 density functionals we tested, M06-2X has the best performance for a hybrid functional, and MN15-L has the best performance for a local functional. Thermal rate constants of the elementary reactions involved in the reaction mechanism are calculated using M06-2X and multistructural canonical variational transition state theory with the small-curvature tunneling approximation (MS-CVT/SCT). The pressure dependence of unimolecular isomerization reactions is treated with system-specific quantum RRK theory (SS-QRRK) and the Lindemann-Hinshelwood mechanism.

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Ab initio study on the mechanism of the HCO+O2→HO2+CO reaction

Cited by 25 publications

References 15 publications

Photochemical reactions of methyl and ethyl nitrate: a dual role for alkyl nitrates in the nitrogen cycle

Photochemical reactions of methyl and ethyl nitrate: a dual role for alkyl nitrates in the nitrogen cycle

Experimental Evidence of Dioxole Unimolecular Decay Pathway for Isoprene-Derived Criegee Intermediates

Silane-initiated nucleation in chemically active plasmas: validation of density functionals, mechanisms, and pressure-dependent variational transition state calculations

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