The origin of the large bending enhancement of the reaction of C2H2+ with methane: the effects of bending momentum, ruling out the precursor mechanism, and steps toward “Polanyi rules” for polyatomic reactions

Li, Jianbo; Anderson, Scott L.

doi:10.1039/b908328f

Cited by 6 publications

(6 citation statements)

References 35 publications

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“…One of the motivations for doing trajectory simulations is to explore the aspects of reaction dynamics that are not experimentally accessible. In previous trajectory simulations of ion−molecule reactions, we often found that collision orientation is critical for reaction. ,,,− For example, we recently reported trajectory simulations of protonated tyrosine and 1 O 2 at E col = 3.0 eV . Despite the fact that the reaction of TyrH + + 1 O 2 → [Tyr-H] + + H 2 O 2 is exoergic, the reaction efficiency is quite low (less than 3%).…”

Section: Resultsmentioning

confidence: 99%

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Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects

et al. 2011

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The reaction of protonated methionine with the lowest electronically excited state of molecular oxygen O(2)(a(1)Δ(g)) was studied in a guided ion beam apparatus, including the measurement of reaction cross sections over a center-of-mass collision energy (E(col)) range of 0.1-2.0 eV. A series of electronic structure and RRKM calculations were used to examine the properties of various complexes and transition states that might be important along the reaction coordinate. Only one product channel is observed, corresponding to generation of hydrogen peroxide via transfer of two hydrogen atoms (H2T) from protonated methionine to singlet oxygen. At low collision energies, the reaction approaches the collision limit and may be mediated by intermediate complexes. The reaction shows strong inhibition by collision energy, and becomes negligible at E(col) > 1.25 eV. A large set of quasi-classical direct dynamics trajectory simulations were calculated at the B3LYP/6-21G level of theory. Trajectories reproduced experimental results and provided insight into the mechanistic origin of the H2T reaction, how the reaction probability varies with impact parameter, and the suppressing effect of collision energy. Analysis of the trajectories shows that at E(col) = 1.0 eV the reaction is mediated by a precursor and/or hydroperoxide complex, and is sharply orientation-dependent. Only 20% of collisions have favorable reactant orientations at the collision point, and of those, less than half form precursor and hydroperoxide complexes which eventually lead to reaction. The narrow range of reactive collision orientations, together with physical quenching of (1)O(2) via intersystem crossing between singlet and triplet electronic states, may account for the low reaction efficiency observed at high E(col).

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Section: Resultsmentioning

confidence: 99%

“…For trajectory visualization, we used the program gOpenMol . Detailed analysis of individual trajectories and statistical analysis of the trajectory ensemble was done with programs written for this purpose, as described previously. ,,− …”

Section: Methodsmentioning

confidence: 99%

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects

et al. 2011

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“…The program gOpenMol was used for trajectory visualization . Analysis of individual trajectories and statistical analysis of the trajectory ensemble was done with programs written for this purpose. ,,− …”

Section: Computational Methodologiesmentioning

confidence: 99%

Dynamics Simulations and Statistical Modeling of Thermal Decomposition of 1-Ethyl-3-methylimidazolium Dicyanamide and 1-Ethyl-2,3-dimethylimidazolium Dicyanamide

Chambreau

Vaghjiani

2014

J. Phys. Chem. A

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Quasi-classical, direct dynamics trajectories were calculated at the B3LYP/6-31G* level of theory, in an attempt to understand decomposition mechanisms of 1-ethyl-3-methylimidazolium dicyanamide (EMIM(+)DCA(-)) and 1-ethyl-2,3-dimethylimidazolium dicyanamide (EMMIM(+)DCA(-)). The trajectories showed many dissociation paths for these two ionic liquids. Using trajectory results as a guide, structures of transition states and products that might be important for decomposition of these two compounds were determined using density functional theory calculations. Rice-Ramsperger-Kassel-Marcus (RRKM) theory was then utilized to examine properties of energized ionic liquids and to determine unimolecular rates for crossing various transition states. On the basis of RRKM modeling, initial decomposition paths for energized EMIM(+)DCA(-) correspond to formation of an N-heterocyclic carbene and acid pair via transfer of the C2 proton of EMIM(+) to DCA(-), and evolution of methylimidazole and ethylimidazole via SN2 alkyl abstraction by DCA(-). Similar decomposition paths were identified for energized EMMIM(+)DCA(-), except that the reactivity of C2 of the imidazolium cation is significantly reduced upon substitution of a methyl group for a hydrogen atom at this position. The present work demonstrates that dynamics simulations, in conjunction with statistical modeling, are able to provide insight into decomposition mechanisms, kinetics, and dynamics for alkylimidazolium-based ionic liquids and to predict product branching ratios and how they vary with decomposition temperatures.

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“…The program gOpenMol was used for trajectory visualization . Detailed analysis of individual trajectories and statistical analysis of the trajectory ensemble was done with programs specifically written for this purpose, ,− available from the corresponding author upon request.…”

Section: Computational Methodologymentioning

confidence: 99%

Thermal Decomposition of 1,5-Dinitrobiuret (DNB): Direct Dynamics Trajectory Simulations and Statistical Modeling

Chambreau

Vaghjiani

2011

J. Phys. Chem. A

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A large set of quasi-classical, direct dynamics trajectory simulations were performed for decomposition of 1,5-dinitrobiuret (DNB) over a temperature range from 4000 to 6000 K, aimed at providing insight into DNB decomposition mechanisms. The trajectories revealed various decomposition paths and reproduced the products (including HNCO, N(2)O, NO(2), NO, and water) observed in DNB pyrolysis experiments. Using trajectory results as a guide, structures of intermediate complexes and transition states that might be important for decomposition were determined using density functional theory calculations. Rice-Ramsperger-Kassel-Marcus (RRKM) theory was then utilized to examine behaviors of the energized reactant and intermediates and to determine unimolecular rates for crossing various transition states. According to RRKM predictions, the dominant initial decomposition path of energized DNB corresponds to elimination of HNNO(2)H via a concerted mechanism where the molecular decomposition is accompanied with intramolecular H-atom transfer from the central nitrogen to the terminal nitro oxygen. Other important paths correspond to elimination of NO(2) and H(2)NNO(2). NO(2) elimination is a simple N-N bond scission process. Formation and elimination of nitramide is, however, dynamically complicated, requiring twisting a -NHNO(2) group out of the molecular plane, followed by an intramolecular reaction to form nitramide before its elimination. These two paths become significant at temperatures above 1500 K, accounting for >17% of DNB decomposition at 2000 K. This work demonstrates that quasi-classical trajectory simulations, in conjunction with electronic structure and RRKM calculations, are able to extract mechanisms, kinetics, dynamics and product branching ratios for the decomposition of complex energetic molecules and to predict how they vary with decomposition temperature.

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The origin of the large bending enhancement of the reaction of C2H2+ with methane: the effects of bending momentum, ruling out the precursor mechanism, and steps toward “Polanyi rules” for polyatomic reactions

Cited by 6 publications

References 35 publications

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects

Dynamics Simulations and Statistical Modeling of Thermal Decomposition of 1-Ethyl-3-methylimidazolium Dicyanamide and 1-Ethyl-2,3-dimethylimidazolium Dicyanamide

Thermal Decomposition of 1,5-Dinitrobiuret (DNB): Direct Dynamics Trajectory Simulations and Statistical Modeling

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The origin of the large bending enhancement of the reaction of C2H2+ with methane: the effects of bending momentum, ruling out the precursor mechanism, and steps toward “Polanyi rules” for polyatomic reactions

Cited by 6 publications

References 35 publications

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a1Δg): Reaction Dynamics and Collision Energy Effects

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a1Δg): Reaction Dynamics and Collision Energy Effects

Dynamics Simulations and Statistical Modeling of Thermal Decomposition of 1-Ethyl-3-methylimidazolium Dicyanamide and 1-Ethyl-2,3-dimethylimidazolium Dicyanamide

Thermal Decomposition of 1,5-Dinitrobiuret (DNB): Direct Dynamics Trajectory Simulations and Statistical Modeling

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Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects

Experimental and Trajectory Study on the Reaction of Protonated Methionine with Electronically Excited Singlet Molecular Oxygen (a¹Δ_g): Reaction Dynamics and Collision Energy Effects