Ab initio study of the addition of atomic carbon with water

Hwang, Der-Yan; Mebel, Alexander M.; Wang, Bo-Cheng

doi:10.1016/s0301-0104(99)00156-1

Cited by 18 publications

(31 citation statements)

References 24 publications

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“…The C + H 2 S triplet energy surface looks very similar to that of the valence isoelectronic C + H 2 O system. 12,13 There are three triplet multiplicity minima with CSH 2 stoichiometry: H 2 SC 1 (C s , 3 A′′), HSCH, 2 (C 1 , 3 A), and H 2 CS, 3 (C s , 3 A′′). These species have been recently studied at a higher level of theory.…”

Section: Resultsmentioning

confidence: 99%

Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels

et al. 2001

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The multichannel C + H 2 S reaction was studied, at room temperature, in a low-pressure fast-flow reactor. Carbon atoms were obtained from the reaction of CBr 4 with potassium atoms. The overall rate constant was found to be (2.1 ( 0.5) × 10 -10 cm 3 molecule -1 s -1 , close to the gas kinetic limit. Absolute product branching ratio was estimated over the channels yielding H atoms probed by resonance fluorescence in the vacuum ultraviolet: H + HCS or HSC (75 ( 25)%. Ab initio studies of the different stationary points relevant to this reaction have been performed at the CCSD(T)/cc-pVTZ//QCISD/cc-pVDZ level. In agreement with the measured rate constant, the insertion transition structure leading to triplet HSCH is found lower in energy than the reactants. The reaction is found to proceed via H 2 SC ( 3 A′′) intermediate that then rearrange to HSCH. On the basis of RRKM calculations, this last species leads mainly to HCS + H products.

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Section: Resultsmentioning

confidence: 99%

Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels

et al. 2001

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“…[3] The reactions of small carbon clusters C n (n < 5) with water in Ar matrices also indicate that neither 3 P-C nor singlet or triplet C 2 react with water, while C 3 species do. [4] A more recent (1999) high-level computational study [CCSD(T)/ 6-311 + GA C H T U N G T R E N N U N G (3df,2p)] by Hwang et al, [5] which incidentally does not cite the remarkable 1983 paper or the matrix-isolation study of Ortman et al, challenges these conclusions by stating that there is a path for 3 P-C to give products that are the same as those from the singlet manifold. This pathway is possible owing to a conical intersection (at the CASSCF/6-311 + G** level; intersystem crossing, ISC) found for the singlet ( 1 A') and triplet ( 3 A) states of 2.…”

Section: S-c (233 Kcal Mol à1mentioning

confidence: 99%

The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Schreiner¹,

Reisenauer²

2006

ChemPhysChem

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We introduce a novel experimental setup for the generation of carbon atoms by means of pulsed laser ablation with a pulse rate optimized to avoid warming of the matrix. The combination of this technique with annealing of the matrix, recooling, and spectral recording (e.g. IR) allowed us to differentiate between the reactivity of triplet and singlet carbon atoms towards water under matrix-isolation conditions. Our experimental procedure assures the relaxation of all unreacted carbon atoms to their triplet ground state in the 10 K matrix before spectral recording. In agreement with CCSD(T)/cc-pVTZ+ZPVE computational data and earlier lower level results, we find that triplet carbon atoms indeed do not react with water, despite their high initial energy. Intersystem crossing of the triplet to singlet states of hydroxy carbene are less important, as the barriers for rearrangement of the initial complex of triplet carbon atoms and water to covalently bound species are too high, and dissociation is more likely. We found no evidence for a direct O--H bond-insertion path for triplet carbon atoms. Self-condensation reactions of triplet carbon atoms are clearly favored and yield carbon clusters that show reactivity of their own. The proposed formation of aldoses in extraterrestrial environments can therefore only derive from "hot" carbon atoms or through photoreactions.

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“…In current astrochemical models the adsorption energy of a carbon atom on ice is taken to be 800 K (Hama & Watanabe 2013). This value has neither been measured nor calculated and could be significantly underestimated as ab-initio calculations lead to a binding energy of the C...H 2 O van der Waals complex equal to 3600 K (Schreiner & Reisenauer 2006;Hwang et al 1999;Ozkan & Dede 2012) and to a binding energy of the C...CH 3 OH van der Waals complex equal to 8400 K (Dede & Ozkan 2012). Then, even if carbon atoms have been shown to react quickly with methanol in the gas phase (Shannon et al 2013), the strength of the C...CH 3 OH complex may prevent reaction if the energy dissipation is efficient enough to stabilize the complex.…”

Section: Introductionmentioning

confidence: 99%

Modelling complex organic molecules in dense regions: Eley–Rideal and complex induced reaction

Ruaud

Loison

Hickson

et al. 2015

Monthly Notices of the Royal Astronomical Society

145

207

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Recent observations have revealed the existence of Complex Organic Molecules (COMs) in cold dense cores and prestellar cores. The presence of these molecules in such cold conditions is not well understood and remains a matter of debate since the previously proposed "warmup" scenario cannot explain these observations. In this article, we study the effect of EleyRideal and complex induced reaction mechanisms of gas-phase carbon atoms with the main ice components of dust grains on the formation of COMs in cold and dense regions. Based on recent experiments we use a low value for the chemical desorption efficiency (which was previously invoked to explain the observed COM abundances). We show that our introduced mechanisms are efficient enough to produce a large amount of complex organic molecules in the gas-phase at temperatures as low as 10K.

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Ab initio study of the addition of atomic carbon with water

Cited by 18 publications

References 24 publications

Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels

Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels

The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Modelling complex organic molecules in dense regions: Eley–Rideal and complex induced reaction

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Ab initio study of the addition of atomic carbon with water

Cited by 18 publications

References 24 publications

Reaction of Carbon Atoms, C (2p2,3P), with Hydrogen Sulfide, H2S (XA1): Overall Rate Constant and Product Channels

Reaction of Carbon Atoms, C (2p2,3P), with Hydrogen Sulfide, H2S (XA1): Overall Rate Constant and Product Channels

The “Non‐Reaction” of Ground‐State Triplet Carbon Atoms with Water Revisited

Modelling complex organic molecules in dense regions: Eley–Rideal and complex induced reaction

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Product

Resources

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Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels

Reaction of Carbon Atoms, C (2p²,³P), with Hydrogen Sulfide, H₂S (XA₁): Overall Rate Constant and Product Channels