Gas-phase atom-radical kinetics of atomic hydrogen reactions with trifluoromethyl, difluoromethylene, and fluoromethylidyne radicals

Tsai, Cheng Ping; McFadden, David L.

doi:10.1021/j100343a048

Cited by 55 publications

(25 citation statements)

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“…Very recently, we have carried out a detailed theoretical investigation 23 on the singlet potential energy surface of the reaction CH + NO 2 . Our calculations were in agreement with the experimental result that H + CO + NO is the almost exclusive product of CH + NO 2 reaction, yet we pointed out that contribution from another product HON+CO should also be considered. Our calculations have highlighted the importance of carrying out ab initio calculations on the reaction mechanism other than just to speculate about it.…”

supporting

confidence: 89%

“…Due to the rather large heat (more than 110 kcal/mol) released from the successive isomerization of reactant R to the isomers 2 and 3, further direct dissociation of FCO in P 1 , FNO in P 2 and FON in P 3 to form the same secondary product P 12 F + CO + NO may be very facile. Then P 12 may be formed via the following four pathways: Path P 12 (4) : R → 1 → 2 → 3 → 4 → P 3 FON + CO → P 12 F + CO + NO It should be pointed out that the species 8, 9, and 10 with very low energies are not included in the PES because we could not locate relevant transition states for them.…”

Section: Transition States and Isomerizationmentioning

confidence: 99%

“…It was suggested that Path (1a) to FCO + NO is a major route, while Path (1b) and Path (2) may be responsible for the observed slight pressure effect. In our calculations, an isomer 10 with formal FCO (1) NO (2) structure is located as an energy minimum lying 68.3 kcal/mol below the reactant R. Yet, it has short CO (1) and NO (2) bond lengths as 1.280 and 1.212 Å, respectively, and the internal O (1) N bond is long as 1.720 Å. Then, isomer 10 is more like an adduct species between FCO and NO rather than one between FC and NO 2 at the terminal O-end.…”

Section: Mechanismmentioning

confidence: 99%

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Theoretical study on reaction mechanism of the CF radical with nitrogen dioxide

Tao

Liu

et al. 2001

J Comput Chem

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ABSTRACT:The singlet potential energy surface of the [CFNO 2 ] system is investigated at the B3LYP and CCSD(T) (single-point) levels to explore the possible reaction mechanism of CF radical with NO 2 . The top attack of C-atom of CF radical at the N-atom of NO 2 molecule first forms the adduct isomer FCNO 2 1 followed by oxygen-shift to give trans-OC(F)NO 2 and then to cis-OC(F)NO 3. Subsequently, the most favorable channel is a direct dissociation of 2 and 3 to product P 1 FCO + NO. The second and third less favorable channels are direct dissociation of 3 to product P 2 FNO + CO and isomerization of 3 to a complex NOF. . .CO 4, which can easily dissociate to product P 3 FON + CO, respectively. The large exothermicity released in these processes further drives most of the three products P 1 , P 2 , and P 3 to take secondary dissociation to the final product P 12 F + CO + NO. Another energetically allowed channel is formation of product P 4 1 NF + CO 2 , yet it is much less competitive than P 1 , P 2 , P 3 , and P 12 . The present calculations can well interpret one recent experimental fact that the title reaction is quite fast yet still much slower than the analogous reaction CH + NO 2 . Also, the results presented in this article may be useful for future product distribution analysis of the title reaction as well as for the analogous CCl and CBr reactions.

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supporting

confidence: 89%

Section: Transition States and Isomerizationmentioning

confidence: 99%

Section: Mechanismmentioning

confidence: 99%

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Theoretical study on reaction mechanism of the CF radical with nitrogen dioxide

Tao

Liu

et al. 2001

J Comput Chem

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“…In this region, CF x does not serve as a catalyst, but rather is reduced to CF xϪ1 in the presence of H. The transition of reaction ͑1͒ from the high-pressure limit to the pressure dependent regime occurs at approximately 300 mTorr. 35 Tsai and McFadden [38][39][40] have proposed that the reaction of CF x and H first forms a complex (CHF x *) which either dissociates resulting in the abstraction of a F atom by H to form HF:…”

Section: Discussionmentioning

confidence: 99%

Macromolecule formation in low density CF4 plasmas: The influence of H2

Schabel

Peterson

Muscat

2003

Journal of Applied Physics

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High molecular weight fluorocarbon species are regarded as important contributors to the nucleation of films and particulates in fluorocarbon plasmas. The chemical reaction mechanisms by which fluorocarbon macromolecules form within a plasma are generally unknown. To elucidate these mechanisms, experiments were conducted in a rf capacitively coupled discharge in a Gaseous Electronics Conference reference cell. The relationships between macromolecule growth and plasma pressure, power, flow rate, and the fraction of H 2 in the CF 4 gas feed are identified. Macromolecule growth was found to increase with increased pressure and rf power, and decreased flow rate. A set of electron-induced dissociation and radical-recombination reactions are simulated using Chemkin-Aurora, a commercially available plasma chemistry model, and are in good agreement with the experimental results of macromolecule growth. We show that a primary mechanism by which fluorocarbon macromolecules form in a plasma occurs by electron-induced dissociation of a fluoroalkane to produce a fluoroalkyl radical and a fluorine atom, followed by a three-body radical-radical recombination reaction with CF 3 . Hydrogen is shown to have a profound effect on this reaction sequence by reducing the gas phase atomic fluorine concentration through the formation of HF which in turn increases the CF 3 concentration available to participate in the macromolecule growth process. At moderate levels of hydrogen in the feed gas (Ͻ20%), macromolecule growth is directly correlated with the fraction of hydrogen in the feed gas. At high concentrations of hydrogen, hydrofluorocarbon and hydrocarbon growth occurs in the plasma at the expense of fluorocarbon macromolecule growth. The conditions under which the formation of these species occurs is consistent with observations in the literature of dramatic reductions in silicon dioxide etching rate. The transition between the formation of fluorocarbon macromolecules and hydrocarbon species in a CF 4 /H 2 plasma is shown to be fundamental to understanding the growth process of each class of species within the plasma.

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“…The existence of H 2 O (g) in the gas mixture turned out to enhance DRE by 6.3%. Both OH radical and H atom, generated from the direct photolysis of H 2 O (g) [52], might account for the enhanced DRE [52][53][54][55][56]: …”

Section: Effect Of H 2 O(g)mentioning

confidence: 99%