scholarly journals Free Radical Isomerizations in Acetylene Bromoboration Reaction

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2501
Author(s):  
Hugo Semrád ◽  
Ctibor Mazal ◽  
Markéta Munzarová
Keyword(s):  
Activation Energy ◽  
Free Energy ◽  
Potential Energy Surfaces ◽  
Energy Profile ◽  
Solvation Model ◽  
Weakly Bound ◽  
Bond Rotation ◽  
Weakly Bound Complexes ◽  
Energy Surfaces ◽  
Radical Attack

The experimentally motivated question of the acetylene bromoboration mechanism was addressed in order to suggest possible radical isomerization pathways for the syn-adduct. Addition–elimination mechanisms starting with a bromine radical attack at the “bromine end” or the “boron end” of the C=C bond were considered. Dispersion-corrected DFT and MP2 methods with the SMD solvation model were employed using three all-electron bases as well as the ECP28MWB ansatz. The rate-determining, elimination step had a higher activation energy (12 kcal mol−1) in case of the “bromine end” attack due to intermediate stabilization at both the MP2 and DFT levels. In case of the “boron end” attack, two modes of C–C bond rotation were followed and striking differences in MP2 vs. DFT potential energy surfaces were observed. Employing MP2, addition was followed by either a 180° rotation through an eclipsed conformation of vicinal bromine atoms or by an opposite rotation avoiding that conformation, with 5 kcal mol−1 of elimination activation energy. Within B3LYP, the addition and rotation proceeded simultaneously, with a 9 (7) kcal mol−1 barrier for rotation involving (avoiding) eclipsed conformation of vicinal bromines. For weakly bound complexes, ZPE corrections with MP2 revealed significant artifacts when diffuse bases were included, which must be considered in the Gibbs free energy profile interpretation.

Chirality of weakly bound complexes: The potential energy surfaces for the hydrogen-peroxide−noble-gas interactions

2014 ◽  
Vol 141 (13) ◽  
pp. 134309 ◽  
Author(s):  
L. F. Roncaratti ◽  
L. A. Leal ◽  
F. Pirani ◽  
V. Aquilanti ◽  
G. M. e Silva ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Noble Gas ◽  
Weakly Bound ◽  
Weakly Bound Complexes ◽  
Gas Interactions ◽  
Energy Surfaces

scholarly journals Active learning of potential-energy surfaces of weakly bound complexes with regression-tree ensembles

2021 ◽  
Vol 155 (14) ◽  
pp. 144109
Author(s):  
Yahya Saleh ◽  
Vishnu Sanjay ◽  
Armin Iske ◽  
Andrey Yachmenev ◽  
Jochen Küpper
Keyword(s):  
Active Learning ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Regression Tree ◽  
Weakly Bound ◽  
Weakly Bound Complexes ◽  
Energy Surfaces

Symmetry-adapted perturbation theory of potential-energy surfaces for weakly bound molecular complexes

1994 ◽  
Vol 307 ◽  
pp. 135-151 ◽  
Author(s):  
Tatiana Cwiok ◽  
Bogumil Jeziorski ◽  
Wlodzimierz Kolos ◽  
Robert Moszynski ◽  
Krzysztof Szalewicz
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Molecular Complexes ◽  
Weakly Bound ◽  
Energy Surfaces

The insertion of germylene into the H—H bond; rate constant limits and thermochemistry. Ab initio and DFT calculations on the reactions of GeH2 and SiH2 with H2

2000 ◽  
Vol 78 (11) ◽  
pp. 1428-1433 ◽  
Author(s):  
Rosa Becerra ◽  
Sergey E Boganov ◽  
Mikhail P Egorov ◽  
Valery I Faustov ◽  
Oleg M Nefedov ◽  
...  
Keyword(s):  
Activation Energy ◽  
Ab Initio ◽  
Potential Energy Surfaces ◽  
Elevated Temperatures ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Activation Parameters ◽  
Laser Flash ◽  
Bimolecular Reaction ◽  
Energy Surfaces

The technique of laser flash photolysis in the gas-phase has been used to set limits on the rate constants for the bimolecular reaction of germylene (GeH2) with deuterium (D2) at both ambient and elevated temperatures (585 K). These limits show that the activation energy for the insertion of GeH2 into the H—H bond is at least 19 (±6) kJ mol–1. Thermochemical arguments place the activation energy approximately in the range 63–84 kJ mol–1. DFT B3LYP/6-311++G(3df,2pd) and ab initio QCISD(T)/6-311G++(3df,2pd)//QCISD/6-311G(d,p) calculations have been carried out on the potential energy surfaces of reactions ZH2 + H2 [Formula: see text] ZH4 (Z= Ge, Si). Both methods predict the same mechanisms for germylene and silylene insertion which include formation of loose prereaction complexes and transition states of similar structure. The prereaction complex is only about half as strong in the case of germylene (ΔH (298 K) = –9 (–11) kJ mol–1) as in the case of silylene (ΔH (298 K) = –16 (–21) kJ mol–1) (QCISD values cited with B3LYP values in parentheses). The differences in activation energies are even more significant. Germylene insertion has a very high barrier of 58 (56) kJ mol–1 compared to that of silylene 13 (6) kJ mol–1. Calculated activation parameters for both reactions are in reasonable consistency with experimental results. Reasons for the enhanced H—H insertion barrier for germylene compared with silylene are discussed.Key words: laser flash photolysis, germylene, silylene, deuterium, activation energy, thermochemistry, ab initio calculation, DFT B3LYP calculation.

Quantum Simulations of Preferable H2O Dissociation Pathway on the Ru-Alloyed Pt(111) Surface Based on Density Functional Theory

2020 ◽  
Vol 840 ◽  
pp. 495-500
Author(s):  
Victor Reynaldi ◽  
Wahyu Tri Cahyanto ◽  
Farzand Abdullatif
Keyword(s):  
Activation Energy ◽  
Density Functional Theory ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Reaction Pathways ◽  
Dissociation Pathway ◽  
Reaction Route ◽  
Functional Theory ◽  
Energy Surfaces ◽  
Pes Scan

Reaction pathways for a water molecule dissociation (H2Oads) to form hydroxyl (OHads) and hydrogen (Hads) on the Ru-alloyed Pt(111) surface were computationally modelled on the basis of density functional theory (DFT). The aim of this study was to evaluate whether or not such a reaction can take place and to determine the most probable route for this reaction. To get the answer, we calculated the potential energy surfaces (PES) of the proposed reaction pathways. From the results of the PES scan, we then obtained the most preferential pathway for H2O dissociation, i.e., the reaction route with an activation energy of 0.72 eV. This activation energy value is lower than the value of pure Pt (111), the surface at which H2O dissociation can occur in the real system. Thus, it can be said that water splitting may be easier when catalyzing Ru-alloyed surfaces compared to pure Pt catalysts.

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