MCSCF/CI investigation of the low-lying potential energy surfaces of the formyloxyl radical, HCO2.cntdot.

Feller, David; Huyser, Earl S.; Borden, Weston Thatcher; Davidson, Ernest R.

doi:10.1021/ja00344a007

Cited by 107 publications

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“…Our CASSCF [75] -optimized geometric parameters and relative energies are comparable with other results from ab initio calculations. [84,86,87] Our QCISD(T) calculation for the transition structure for the hydrogen atom loss from HCOO (TS19, Figure 6) predicts an energy barrier of 4.9 kcal mol À1 at 0 K, which is about 5 kcal mol À1 lower than that predicted by Feller et al [84] Inclusion of the ZPVE corrections lowers this energy barrier to only 0.4 kcal mol…”

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confidence: 62%

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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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confidence: 62%

“…The dissociation of the HCOO radical into H and CO 2 , which has also been studied theoretically by Feller et al, [84] is undergone by the so-called s radical of HCOO, which has two low-lying electronic states of C 2v symmetry, namely 2 B 2 and 2 A 1 . In addition, these two states yield the 2 A' state after lowering the molecular symmetry to the C s group.…”

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confidence: 94%

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

1999

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“…Please note that the product of Reaction (1) (HCOO) decomposes to H + CO 2 , whereas the product of Reaction (2) (HOCO) decomposes to HO + CO, which are of great atmospheric relevance. [17][18][19][20][21][22][23] …”

Section: à3mentioning

confidence: 99%

“…These decomposition reactions have already been reported in the literature [17][18][19][20][21][22][23] and therefore they are not considered herein.…”

Section: Introductionmentioning

confidence: 99%

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Anglada

González

2009

ChemPhysChem

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The effect of a single water molecule on the reaction mechanism of the gas-phase reaction between formic acid and the hydroxyl radical was investigated with high-level quantum mechanical calculations using DFT-B3LYP, MP2 and CCSD(T) theoretical approaches in concert with the 6-311+G(2df,2p) and aug-cc-pVTZ basis sets. The reaction between HCOOH and HO has a very complex mechanism involving a proton-coupled electron transfer process (pcet), two hydrogen-atom transfer reactions (hat) and a double proton transfer process (dpt). The hydroxyl radical predominantly abstracts the acidic hydrogen of formic acid through a pcet mechanism. A single water molecule affects each one of these reaction mechanisms in different ways, depending on the way the water interacts. Very interesting is also the fact that our calculations predict that the participation of a single water molecule results in the abstraction of the formyl hydrogen of formic acid through a hydrogen atom transfer process (hat).

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“…[8][9][10] It also presents theoretical challenges owing to its two low-lying excited states, which strongly mix and result in a strong pseudo-Jahn-Teller (PJT) coupling that may or may not distort the ground-state equilibrium geometry from C 2V symmetry. [11][12][13][14][15][16] This coupling renders the accurate computation of the geometry and vibronic structure of this species difficult. In this paper, we characterize the vibronic structure of the HCO 2 and DCO 2 radicals using slow photoelectron velocity-map imaging (SEVI) 17 in combination with a theoretical treatment using a quasidiabatic Hamiltonian approach parametrized by high-level ab initio calculations.…”

Section: Introductionmentioning

confidence: 99%

Vibronic Structure of the Formyloxyl Radical (HCO₂) via Slow Photoelectron Velocity-Map Imaging Spectroscopy and Model Hamiltonian Calculations

et al. 2009

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We report high-resolution photoelectron spectra of HCO 2 -and DCO 2 -obtained with slow photoelectron velocity-map imaging. Well-resolved photodetachment transitions to the 2 A 1 and 2 B 2 states of the neutral radicals were observed. In addition, vibronic levels of the HCO 2 and DCO 2 radicals with up to 2000 cm -1 of internal energy were calculated using a quasidiabatic Hamiltonian approach and high-level ab initio calculations. Spectral simulations using the calculated levels were found to be in excellent agreement with the experimental spectra and used to assign many of its features. This study unambiguously determined that the 2 A 1 state is the ground state of both HCO 2 and DCO 2 , in contrast to earlier work that indicated the 2 B 2 state was the ground state for DCO 2 . For both isotopologs, the 2 B 2 state is a very low-lying excited state with term energies of T 0 ) 318 ( 8 cm -1 for HCO 2 and T 0 ) 87 ( 8 cm -1 for DCO 2 . The adiabatic electron affinities are determined to be EA(HCO 2 ) ) 3.4961 ( 0.0010 eV and EA(DCO 2 ) ) 3.5164 ( 0.0010 eV.

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MCSCF/CI investigation of the low-lying potential energy surfaces of the formyloxyl radical, HCO2.cntdot.

Cited by 107 publications

References 0 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

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Vibronic Structure of the Formyloxyl Radical (HCO₂) via Slow Photoelectron Velocity-Map Imaging Spectroscopy and Model Hamiltonian Calculations

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MCSCF/CI investigation of the low-lying potential energy surfaces of the formyloxyl radical, HCO2.cntdot.

Cited by 107 publications

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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

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Vibronic Structure of the Formyloxyl Radical (HCO2) via Slow Photoelectron Velocity-Map Imaging Spectroscopy and Model Hamiltonian Calculations

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Vibronic Structure of the Formyloxyl Radical (HCO₂) via Slow Photoelectron Velocity-Map Imaging Spectroscopy and Model Hamiltonian Calculations