A Computational Study on the Addition of HONO to Alkynes toward the Synthesis of Isoxazoles; a Bifurcation, Pseudopericyclic Pathways and a Barrierless Reaction on the Potential Energy Surface

2017 ◽  
Vol 82 (17) ◽  
pp. 8873-8881 ◽  
Author(s):  
Ang Zuo ◽  
David M. Birney
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Computational Study

Conformational analysis of enantiomerization coupled to internal rotation in triptycyl-n-helicenes

2019 ◽  
Vol 21 (21) ◽  
pp. 11395-11404
Author(s):  
Abel Carreras ◽  
Luca Fuligni ◽  
Pere Alemany ◽  
Miquel Llunell ◽  
Josep Maria Bofill ◽  
...  
Keyword(s):  
Potential Energy ◽  
Conformational Analysis ◽  
Potential Energy Surface ◽  
Internal Rotation ◽  
Energy Surface ◽  
Computational Study ◽  
Reaction Coordinate

We present a computational study of a reduced potential energy surface (PES) to describe enantiomerization and internal rotation in three triptycyl-n-helicene molecules, centering the discussion on the issue of a proper reaction coordinate choice.

scholarly journals Isomerization and Fragmentation Reactions on the [C2SH4] Potential Energy Surface. The Metastable Thione-S-Methylide Isomer

2020 ◽  
Author(s):  
Zoi Salta ◽  
Marc E. Segovia ◽  
Aline Katz ◽  
Nicola Tasinato ◽  
Vincenzo Barone ◽  
...  
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Computational Study ◽  
Experimental Information ◽  
Reaction Scheme ◽  
Ring Closure ◽  
Complete Analysis

Thione S-methylide (TSM), the parent species of the thiocarbonyl ylide family, is a 1,3-dipolar, planar species on the [C2SH4] potential energy surface (PES), which has not shared the richness of studies dedicated to its isomers, the cyclic thiirane (THI), and the keto-enol pair vinyl thiol (VTH)/thioacetaldehyde (THA). While the conrotatory ring closure reaction toward THI was studied in the ‘90s, no complete analysis of the PES is available in the literature. In the present paper, we report a computational study of the reaction scheme linking all species on that PES. We employ several levels of calculation, ranging from density functional theory (DFT), through CCSD(T) based composite schemes, to CASSCF/CASPT2 multi-reference procedures, to find the best description of TSM, its isomers, and the transition states (TSs) ruling their interconversion. Fragmentation of TSM, THA and THI were investigated and compared to the available experimental information. We found that the B2PLYP-D3 functional, contrary to M06-2XD3 or B97X-D, describes well the geometry of both TSM and the transition state connecting it to THI. The reverse barrier, from THI to TSM, amounts to 52.2 kcal mol-1 (to be compared to 17.6 kcal mol-1 for the direct one), thus explaining why, in general, thiocarbonyl ylides cannot be prepared from thiiranes. Conversion of THI to VTH implies also a large barrier, explaining why the reaction has been observed only at high temperatures. The fragmentation of THI to S(3P) or S(1D) and ethylene was also explored, together with the decomposition to H2S plus acetylene. Open species, both in triplet and singlet states, were identified as intermediates in the fragmentations, and their energies were found to be lower than the transition state for the isomerization of THI to VTH, thus explaining the preference for fragmentation over isomerization at relatively low temperatures.

scholarly journals Computational study of the rovibrational spectrum of H2O-HF

2021 ◽  
Author(s):  
Dominika VIGLASKA ◽  
Xiao-Gang Wang ◽  
Tucker CARRINGTON ◽  
David Tew
Keyword(s):  
Experimental Data ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Energy Surface ◽  
Computational Study ◽  
Energy Levels ◽  
Dissociation Limit ◽  
Lanczos Algorithm ◽  
Vibrational States

In this paper we report rovibrational energy levels, transition frequencies, and intensities computed for H2O-HF using a new ab initio potential energy surface and compare with available experimental data. We use the rigid monomer approximation. A G4 symmetry-adapted Lanczos algorithm and an uncoupled product basis are employed. The rovibrational levels are computed up to J = 4. The new analytic 9-D potential is �t to 39771 counterpoise corrected CCSD(T)(F12*)/augcc- pVTZ energies and reduces to the sum of uncoupled H2O and HF potentials in the dissociation limit. On the new potential better agreement with experiment is obtained by re-assigning the R(1) transitions of two vibrational states.

Computational study on the mechanisms and kinetics of the CH2CCl + O2 reaction

2020 ◽  
Vol 98 (8) ◽  
pp. 395-402
Author(s):  
Yunju Zhang ◽  
Bing He ◽  
Yuxi Sun
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Pressure Dependence ◽  
Rate Constants ◽  
Reaction Mechanisms ◽  
Energy Surface ◽  
Computational Study ◽  
Tddft Calculations ◽  
Temperature And Pressure ◽  
Kinetics Of

The potential energy surface for the CH2CCl + O2 reaction has been investigated by using the CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p) method. Two type reaction mechanisms have been located. The H-abstraction of CH2CCl by O2 generates CHCCl + HO2 surmounting a 20.86 kcal/mol barrier. The addition between O2 and CH2CCl proceeds to an intermediate CH2CClO2 (IM1t and IM1c) without a barrier, which can further dissociate or isomerize to various products with the complicated processes. The temperature and pressure dependence rate constants for the CH2CCl + O2 reaction were computed by means of multi-channel RRKM-TST theory. Moreover, TDDFT calculations imply that IM1t, IM1c, IM2, IM4, IM5t, and IM5c will photolyze under the sunlight.

scholarly journals Computational Study of the Ro-Vibrational Spectrum of CO-CO2

2019 ◽  
Author(s):  
Eduardo Castro-Juárez, ◽  
Xiaogang Wang ◽  
Tucker Carrington ◽  
Ernesto Quintas Sanchez ◽  
Dawes, Richard
Keyword(s):  
Potential Energy ◽  
Vibrational Spectrum ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Computational Study ◽  
Experimental Results ◽  
Intermolecular Potential ◽  
Rotational Constants ◽  
Out Of Plane ◽  
Vibrational Energies

<p>We report an accurate intermolecular potential energy surface for CO-CO2. We compute and assign many ro-vibrational energies and wavefunctions For both isomers, the fundamental transition frequencies agree well with previous experimental results. The rotational constants also agree well with their experimental counterparts. Vibration along the out-of-plane coordinates is very floppy.<br></p>

Formation of a pre-reaction hydrogen-bonded complex and its significance in the potential energy surface of the OH + SO2→ HOSO2 reaction: A computational study

2017 ◽  
Vol 16 (05) ◽  
pp. 1750046 ◽  
Author(s):  
Vijay M. Miriyala ◽  
Priya Bhasi ◽  
Zanele P. Nhlabatsi ◽  
Sanyasi Sitha
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Computational Study ◽  
Stationary Points ◽  
Second Step ◽  
Computational Calculations ◽  
Reaction Complex ◽  
Hydrogen Bonded

Using computational calculations, we have revisited the potential energy surface (PES) of the reaction between OH and SO2, which is believed as the rate-limiting step in the atmospheric formation of H2SO4. In this work, we report for the first time the presence of a pre-reaction hydrogen-bonded complex between OH and SO2 in the reaction PES. Based on this finding, it has been shown that the reaction can be considered as a two-step process in which the first step is the formation of the pre-reaction complex and the second step is the transformation of this complex to the product. It was observed that due to the presence of this pre-reaction complex as a potential well in the reaction PES, the barrier height got increased by around two-fold for the second step. Based on this observation, it has been proposed that the kinetics of the reaction is going to be affected. Also based on the analysis of the geometries of this pre-reaction complex and the transition state, it has been argued that the step involving the transformation of this pre-reaction complex to the product via the transition state is going to be the slowest step as this transformation involves large structural changes of the stationary points involved.

scholarly journals Computational study of the rovibrational spectrum of CO2–N2

2020 ◽  
Vol 22 (39) ◽  
pp. 22674-22683 ◽  
Author(s):  
Ernesto Quintas-Sánchez ◽  
Richard Dawes ◽  
Xiao-Gang Wang ◽  
Tucker Carrington
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Computational Study ◽  
Atmospherically Relevant

A new potential energy surface for the atmospherically relevant CO2–N2 complex was constructed and used to compute rovibrational levels.

Potential energy surface of the cation–neutral hydroamination reaction: a computational study on the role of an ion–molecule complex in the reaction pathway

Tetrahedron ◽  
2014 ◽  
Vol 70 (43) ◽  
pp. 7906-7911
Author(s):  
Sanyasi Sitha ◽  
Linda L. Jewell ◽  
Priya Bhasi ◽  
Zanele P. Nhlabatsi ◽  
Vijay M. Miriyala
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Computational Study ◽  
Reaction Pathway

scholarly journals Isomerization and Fragmentation Reactions on the [C2SH4] Potential Energy Surface. The Metastable Thione-S-Methylide Isomer

2020 ◽  
Author(s):  
Zoi Salta ◽  
Marc E. Segovia ◽  
Aline Katz ◽  
Nicola Tasinato ◽  
Vincenzo Barone ◽  
...  
Keyword(s):  
Potential Energy ◽  
Transition State ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Computational Study ◽  
Experimental Information ◽  
Reaction Scheme ◽  
Ring Closure ◽  
Complete Analysis

Thione S-methylide (TSM), the parent species of the thiocarbonyl ylide family, is a 1,3-dipolar, planar species on the [C2SH4] potential energy surface (PES), which has not shared the richness of studies dedicated to its isomers, the cyclic thiirane (THI), and the keto-enol pair vinyl thiol (VTH)/thioacetaldehyde (THA). While the conrotatory ring closure reaction toward THI was studied in the ‘90s, no complete analysis of the PES is available in the literature. In the present paper, we report a computational study of the reaction scheme linking all species on that PES. We employ several levels of calculation, ranging from density functional theory (DFT), through CCSD(T) based composite schemes, to CASSCF/CASPT2 multi-reference procedures, to find the best description of TSM, its isomers, and the transition states (TSs) ruling their interconversion. Fragmentation of TSM, THA and THI were investigated and compared to the available experimental information. We found that the B2PLYP-D3 functional, contrary to M06-2XD3 or B97X-D, describes well the geometry of both TSM and the transition state connecting it to THI. The reverse barrier, from THI to TSM, amounts to 52.2 kcal mol-1 (to be compared to 17.6 kcal mol-1 for the direct one), thus explaining why, in general, thiocarbonyl ylides cannot be prepared from thiiranes. Conversion of THI to VTH implies also a large barrier, explaining why the reaction has been observed only at high temperatures. The fragmentation of THI to S(3P) or S(1D) and ethylene was also explored, together with the decomposition to H2S plus acetylene. Open species, both in triplet and singlet states, were identified as intermediates in the fragmentations, and their energies were found to be lower than the transition state for the isomerization of THI to VTH, thus explaining the preference for fragmentation over isomerization at relatively low temperatures.

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