A FT IR study of a transitory product in the gas-phase ozone-ethylene reaction

Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P.

doi:10.1021/j150608a020

Cited by 66 publications

(65 citation statements)

References 2 publications

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“…Experimental highpressure limit rates are unknown for these reactions. Conditions for known experiments are around the standard conditions of 298 K and 1 atm [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Considerations at higher temperatures and pressures have never been made for these reactions, but will be considered here in the low-temperature combustion of dimethyl ether.…”

Section: Resultsmentioning

confidence: 99%

“…From this work, we know that the barrier to formation of H _ CO and ÁOH (30.8 kcal mol À1 ) [74] is less favourable than the cyclic rearrangement to form dioxirane (19.0 kcal mol À1 ) [15]. However, ÁOH formation in ethylene ozonolysis has been detected experimentally [40][41][42][43][44][45][46][47]. The measured branching ratio for production of ÁOH under atmospheric conditions is about 12-40% [48].…”

Section: Molecular Physics 383mentioning

confidence: 99%

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First-principles-derived kinetics of the reactions involved in low-temperature dimethyl ether oxidation

Andersen¹,

Carter²

2008

Molecular Physics

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Spin-polarised density functional theory (DFT-B3LYP) energies, harmonic vibrational frequencies, and moments of inertia are used to construct modified Arrhenius rate expressions for elementary steps in chain-propagation and chain-branching pathways for dimethyl ether combustion. Barrierless reactions were treated with variational RRKM theory, and global kinetics were modeled using master equation and perfectly stirred reactor simulations. Our kinetics analysis suggests that the bottleneck along the chain propagation path is the isomerisation of CH 3 OCH 2 OO, contrary to earlier interpretations. Comparing the rate constants for competing decomposition pathways of the key chain-branching intermediate hydroperoxymethyl formate (HPMF), we find that formation of formic acid and the atmospherically relevant Criegee intermediate (CH 2 OO) via a H-bonded adduct may be more favourable than O-O bond scission. Since the latter forms a source of a second OH radical beyond that supplied in chain propagation, which is necessary for explosive combustion, the more favourable pathway to formic acid may inhibit autoignition of the fuel. We predict that the HPMF O-O scission product, OCH 2 OC(¼O)H, most likely directly dissociates to HCO þ HC(¼O)OH. This implies an overabundance of CO at 550-700 K, since HC(¼O)OH is a fairly stable product in this temperature range and facile H abstraction from HCO leads to CO. We find that CO 2 product yields are sensitive to the creation of CH 2 OO and that creation of CH 2 OO is competitive with the O-O scission reaction.

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Section: Resultsmentioning

confidence: 99%

Section: Molecular Physics 383mentioning

confidence: 99%

First-principles-derived kinetics of the reactions involved in low-temperature dimethyl ether oxidation

Andersen¹,

Carter²

2008

Molecular Physics

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“…These values indicate that M14 will be the major product of the SOZ cleavage. Hydroxymethyl formate was initially identified as a transitory product in the gas-phase ozonolysis of ethylene, [21,26,82] and was supposed to be formed as a product of the carbonyl oxide formaldehyde reaction, but further experimental work indicated that this transitory product could be hydroperoxymethyl formate, [32,33] although the mechanism for its formation is only speculative. [32] The energy barriers for the key structures TS11 and TS12, relative to M10 (SOZ), computed at CASPT2 levels of theory, differ by 4.4 and 10.7 kcal mol À1 respectively from the QCISD(T) values (see footnote [c] in Table 2).…”

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confidence: 99%

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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“…Despite numerous studies of this reaction by different spectroscopic techniques the precise mechanism of the reaction is still unknown [2][3][4][5][6][7][8][9][10]. This is also true for the dissociation of the secondary ozonide.…”

Section: IImentioning

confidence: 99%

“…Another drawback of this work is that the assignment of the spectral band was not supported by high level ab initio calculations which were also not possible at that time. In the early 1980's Niki et al [4] investigated gaseous products of ethene ozonization reaction. The reaction occurred in the gas phase and no separation of the products was made.…”

Section: IImentioning

confidence: 99%

Matrix isolation FTIR spectroscopical study of ethene secondary ozonide

2007

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Abstract:A new method is used for the separation of ethene secondary ozonide (SOZ) from the other products of ethene ozonization reaction. The reaction was performed in the neat films of the reactants at 77 K. Ethene SOZ was separated from other products of the reaction by vacuum distillation at 190-210 K and analyzed by means of the matrix isolation IR absorption spectroscopy. Spectroscopic data from photolysis of the matrix isolated ozonide was used as an argument for assignment of the infrared spectral bands either to ethene SOZ or to other products of the reaction. The spectra of ethene SOZ isolated in the Ar matrix were analyzed by combining experimental results with the theoretical calculations performed at the MP2 6-311+G (3df, 3pd) level. A new assignment of some experimental fundamental bands is proposed taking in to account the Fermi resonance between CH stretch and the five membered ring vibrations. For the first time more than 30 weak infrared absorption bands were observed and assigned to various combination vibrations and overtones. By using new spectral information concerning the overtones and the combination bands it is concluded that the dissociation of unstable ethene SOZ involving breaking of any of the four CO bonds of the five membered ring of ethene SOZ has low probability. Dissociation of the ring starts from breaking of the OO bond.

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A FT IR study of a transitory product in the gas-phase ozone-ethylene reaction

Cited by 66 publications

References 2 publications

First-principles-derived kinetics of the reactions involved in low-temperature dimethyl ether oxidation

First-principles-derived kinetics of the reactions involved in low-temperature dimethyl ether oxidation

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

Matrix isolation FTIR spectroscopical study of ethene secondary ozonide

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