A theoretical insight into the insertion reaction of singlet methylene to the hydrogen molecule

1987 ◽  
Vol 65 (9) ◽  
pp. 1995-1999 ◽  
Author(s):  
M. Ortega ◽  
J. M. Lluch ◽  
A. Oliva ◽  
J. Bertran
Keyword(s):  
Hydrogen Molecule ◽  
Energy Surface ◽  
Correlation Energy ◽  
Geometry Optimization ◽  
Direct Consequence ◽  
Electronic Configuration ◽  
Basis Set ◽  
Insertion Reaction ◽  
Moller Plesset ◽  
Singlet Methylene

The least-motion and non-least-motion energy profiles for the insertion reaction of singlet methylene into the hydrogen molecule have been calculated using the 6-31G* basis set and introducing the correlation energy with the Møller–Plesset perturbation theory and with the MC-SCF technique. From the results obtained the effect of geometry optimization including electron correlation on the shape of the energy surface is discussed. The building up of a bidimensional biconfigurational energy surface has permitted one to interpret the opening of the methylene angle during the least-motion process as a direct consequence of the change in the electronic configuration. The TC-SCF/6-31G* second order transition structure for this forbidden process has been directly located using gradient minimization methods.

scholarly journals A theoretical study of the mechanism of the addition reaction between carbene and azacyclopropane

2010 ◽  
Vol 75 (5) ◽  
pp. 649-657 ◽  
Author(s):  
Xiaojun Tan ◽  
Ping Li ◽  
Weihua Wang ◽  
Gengxiu Zheng ◽  
Qiufen Wang
Keyword(s):  
Potential Barrier ◽  
Energy Surface ◽  
Addition Reaction ◽  
Exothermic Reaction ◽  
Geometry Optimization ◽  
Vibrational Analysis ◽  
Basis Set ◽  
Stationary Points ◽  
Orbital Interactions ◽  
Moller Plesset

The mechanism of the addition reaction between carbene and azacyclopropane was investigated using the second-order Moller-Plesset perturbation theory (MP2). By using the 6-311+G* basis set, geometry optimization, vibrational analysis and the energy properties of the involved stationary points on the potential energy surface were calculated. From the surface energy profile, it can be predicted that there are two reaction mechanisms. The first one (1) is carbene attack at the N atom of azacyclopropane to form an intermediate, 1a (IM1a), which is a barrierfree exothermic reaction. Then, IM1a can isomerize to IM1b via a transition state 1a (TS1a), in which the potential barrier is 30.0 kJ/mol. Subsequently, IM1b isomerizes to a product (Pro1) via TS1b with a potential barrier of 39.3 kJ/mol. The other one (2) is carbene attack at the C atom of azacyclopropane, firstly to form IM2 via TS2a, the potential barrier is 35.4 kJ/mol. Then IM2 isomerizes to a product (Pro2) via TS2b with a potential barrier of 35.1 kJ/mol. Correspondingly, the reaction energy for the reaction (1) and (2) is -478.3 and -509.9 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate.

Theoretical study on the insertion reaction of CH(X2Π) with CH4

1997 ◽  
Vol 75 (7) ◽  
pp. 996-1001 ◽  
Author(s):  
Zhi-Xiang Wang ◽  
Ming-Bao Huang. ◽  
Ruo-Zhuang Liu
Keyword(s):  
Electron Correlation ◽  
Energy Surface ◽  
Theoretical Study ◽  
Reaction Path ◽  
Basis Sets ◽  
Insertion Reaction ◽  
Molecular Orbital Calculations ◽  
Insertion Reactions ◽  
Moller Plesset ◽  
Ch Radical

The CH + CH4 reaction has been studied by means of ab initio molecular orbital calculations incorporating electron correlation with Møller–Plesset perturbation theory up to second and fourth orders with the 6-31G(d,p) and 6-311++G(2d,p) basis sets. An energetically feasible insertion reaction path has been found in the potential energy surface that confirms the experimental proposal for the mechanism of the CH + CH4 reaction. The feature of the mechanism for the CH + CH4 insertion reaction is found to be different from the feature of the mechanisms for the CH + NH3, CH + H2O, and CH + HF insertion reactions, but somewhat similar to that for the CH2 + CH4 insertion reaction. Energetic results for the CH + CH4 reactions are in agreement with experiment. Keywords: CH radical, methane, reaction mechanism.

scholarly journals Accurate global potential energy surface for the ground state of CH2+ by extrapolation to the complete basis set limit

RSC Advances ◽  
2018 ◽  
Vol 8 (25) ◽  
pp. 13635-13642 ◽  
Author(s):  
Lu Guo ◽  
Hongyu Ma ◽  
Lulu Zhang ◽  
Yuzhi Song ◽  
Yongqing Li
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ground State ◽  
Energy Surface ◽  
Correlation Energy ◽  
Basis Set ◽  
Basis Sets ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit

A full three-dimensional global potential energy surface is reported for the ground state of CH2+ by fitting accurate multireference configuration interaction energies calculated using aug-cc-pVQZ and aug-cc-pV5Z basis sets with extrapolation of the electron correlation energy to the complete basis set limit.

scholarly journals Potential Energy Surface (PES) Scan of Gas-Phase L-Proline

2014 ◽  
Vol 38 ◽  
pp. 26-34
Author(s):  
Anouar el Guerdaoui ◽  
Yassine el Kahoui ◽  
Malika Bourjila ◽  
Rachida Tijar ◽  
Abderrahman el Gridani
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Surface ◽  
Conformational Stability ◽  
Geometry Optimization ◽  
Basis Set ◽  
Absolute Minimum ◽  
Pes Scan

We performed here a systematic ab initio calculations on neutral gas-phase L-proline. A total of 8 local minima were located by geometry optimization of the trial structures using density functional theory (DFT) with B3LYP three parameter hybrid potential coupled with the 6-31G)d( basis set. The absolute minimum obtained will be subject to a rigid potential energy surface (PES) scan by rotating its carboxylic group using the same method with more accurate basis set B3LYP/6-311++G(d,p), to get a deeper idea about its conformational stability. The main aim of the present work was the study of the rigidity of the L-proline structure and the puckering of its pyrrolidine ring.

Molecular orbital studies of carbyne reactions: addition and insertion reaction paths for the reaction

1985 ◽  
Vol 63 (7) ◽  
pp. 1689-1693 ◽  
Author(s):  
Ratnakar K. Gosavi ◽  
Imre Safarik ◽  
Otto P. Strausz
Keyword(s):  
Activation Energy ◽  
Potential Energy ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Open Shell ◽  
Basis Set ◽  
Insertion Reaction ◽  
Orbital Theory ◽  
Asymmetric Reaction ◽  
Geometry Analysis

Potential energy hypersurfaces have been studied for the [Formula: see text] addition and insertion reactions by abinitio molecular orbital theory. 6-31G basis set was used for complete geometry optimization of CH, C2H4, the cyclopropyl and allyl radicals as well as the reaction intermediates involved, with the RHF open shell SCF method. CI calculations were then performed at the SCF level optimized geometry. Analysis of the potential energy hypersurfaces predicts, in agreement with reported experimental data, a zero activation energy for the addition reaction via a non least motion, asymmetric reaction path, while the insertion reaction features a computed activation energy of 15 kcal mol−1.

An ab initio study on the reaction of CH(X2π) with CH4

1993 ◽  
Vol 71 (4) ◽  
pp. 512-519 ◽  
Author(s):  
Zhonghua Yu ◽  
Congxiang Chen ◽  
Mingbao Huang
Keyword(s):  
Ab Initio ◽  
Correlation Energy ◽  
Reaction Path ◽  
Addition Reaction ◽  
High Energy ◽  
Insertion Reaction ◽  
Molecular Orbital Calculations ◽  
Configuration Interaction Method ◽  
State Abstraction ◽  
Moller Plesset

The mechanism of the reaction CH(X2π) + CH4 has been investigated by ab initio molecular orbital calculations. Addition, insertion, and abstraction–addition reaction paths have been examined by, in total, five methods of approach. The addition reaction path has a rather high energy barrier. Our calculations have implied that the assumed insertion reaction path does not seem to exist for the reaction CH + CH4, and a two-step mechanism (abstraction–addition reaction path) was then proposed. For the abstraction–addition reaction, the reactants, transition state, intermediates, and products were optimized at the HF/3-21G and HF/6-31G* levels, and vibrational frequencies were calculated at the HF/3-21G level. Electronic correlation energy was estimated by means of the Møller–Plesset perturbation theory and configuration interaction method. The excited-state abstraction reaction was also studied in some detail.

Saddle-point geometries and barriers to internal rotation of formamide : an ab initio study

1980 ◽  
Vol 33 (2) ◽  
pp. 249 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Transition State ◽  
Ground State ◽  
Energy Surface ◽  
Saddle Points ◽  
Geometry Optimization ◽  
Internal Motion ◽  
Basis Set ◽  
Minimal Basis ◽  
Experimental Values ◽  
Extended Basis

By use of a direct transition-state program and the STO-3G minimal basis set, two saddle-points are detected on the energy surface for internal motion of formamide. These correspond mainly to rotation about the C-N bond along with some lengthening of this bond and increased pyramidal distortion at nitrogen as compared with that in the ground state. The STO-3G estimates of the barrier height (34-39 kJ mol-1) are in very poor agreement with experimental values (70-90 kJ mol-1), but 4- 31G energy evaluations for the STO-3G-optimized structures give much better estimates (62-80 kJ mol-1). Contrary to a previous report, use of the 4-31G extended basis set for geometry optimization suggests that only the lower-energy member (NH2 cis to CO) of the above pair is a true transition state for internal motion of formamide; its energy relative to that of the 4-31G-optimized ground state (planar) is 83.5 kJ mol-1, very close to the midpoint of the experimental range. The transition state appears to lie in a region of the 4-31G energy surface that is relatively flat with respect to pyramidal distortion at nitrogen; constraining the amino group to planarity raises the calculated energy by only 6.5kJmol-1.

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