scholarly journals Theoretical Study of Reaction Between Nitrilimine and 1,4 Oxazine 2 Carboxylate by MP2 and DFT Methods

2018 ◽  
Vol 34 (6) ◽  
pp. 2992-2997
Author(s):  
H. El-Hadki ◽  
F. Hlimi ◽  
M. Salah ◽  
K. Marakchi ◽  
N. Komiha ◽  
...  
Keyword(s):  
Energy Surface ◽  
Theoretical Study ◽  
Basis Set ◽  
Dft Methods ◽  
Reactivity Indices ◽  
B3lyp Method ◽  
Transition Structures ◽  
Potential Energy Surface Calculation ◽  
Good Agreement ◽  
Surface Calculation

The regioselectivity of the reaction between phenyldiazen-1-ium-1-ylidene p-tolyl methanide and ethyl 4-benzoyl-4H-benzo [1,4]oxazine-2-carboxylate were studied by means of the DFT/B3LYP method coupled by the 6-31g(d) basis and MP2 in connection with 6-31G(d) and 6-31G+(d,p) basis set. The mechanism of this regioselectif reaction has performed by transition state optimization, evaluation of the potential energy surface, calculation of IRC and reactivity indices. Location and verification of minima and transition structures have been realized by using the Berny's algorithm. The process of formation of the two regioisomers is achieved through concerted and asynchronous mechanism. The results are in good agreement with the experimental data.

A theoretical study on the kinetics for ethanol reaction with formyl radical

2021 ◽  
Vol 11 (1) ◽  
pp. 38-43
Author(s):  
Nguyen Trong Nghia ◽  
Nguyen Duc Trung ◽  
Tran Thi Thoa ◽  
Phan Thi Thuy
Keyword(s):  
Free Radical ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Rate Constant ◽  
Energy Surface ◽  
Theoretical Study ◽  
Single Point ◽  
Renewable Fuels ◽  
Potential Energy Surface Calculation ◽  
Surface Calculation

C2H5OH is one of important renewable fuels. The mechanism for the C2H5OH + HCO reaction has been investigated by a potential energy surface calculation at the B3LYP/aug-cc-pVTZ (optimization) and CCSD(T)/cc-pVTZ (single-point) levels. Our results show that the HCO free radical can abstract the H atoms in the OH group giving CH3CH2O + CH2O or in the CH2 group giving CH3CHOH + CH2O. The rate constant results by TST calculations considering tunneling corrections show that the second pathway is dominate in all the calculation temperature range of 300-2000K.

Quantum chemical computations on rotational isomers of hydrogen nitrite and nitritomethane

1982 ◽  
Vol 381 (1781) ◽  
pp. 443-455 ◽  
Keyword(s):  
Excited States ◽  
Quantum Chemical ◽  
Dipole Moments ◽  
Basis Set ◽  
Electronic Transitions ◽  
Rotational Isomers ◽  
Transition Structures ◽  
Quantum Chemical Computations ◽  
Split Valence ◽  
Good Agreement

Ab initio molecular-orbital computations with a split-valence 4-31G basis set have been carried out on syn- and antiperiplanar conformers of both HONO and H 3 CONO, and on the transition structures in the unimolecular isomerization process. Calculated values of geometric structural and rotational parameters, dipole moments, wavenumbers of vibrational transitions, energies of vertical electronic transitions to both neutral and ionized excited states, and thermodynamic properties are compared with experimental data; generally good agreement is found. No explanation of the anomalous stability of antiperiplanar HONO has been discovered.

scholarly journals DFT Study of the Coordination of N-monochlorosubstituted Derivatives of the N-deprotonated Tautomer of the Biguanide

2020 ◽  
pp. 10-25
Author(s):  
Aïdote François ◽  
Kuevi Urbain Amah ◽  
Kpotin Assongba Gaston ◽  
Atohoun G. Sylvain
Keyword(s):  
Chlorine Atom ◽  
Theoretical Study ◽  
Basis Set ◽  
Imine Nitrogen ◽  
Coordination Sites ◽  
B3lyp Method ◽  
Treatment Of Diabetes ◽  
Experimental Works ◽  
Therapeutic Properties ◽  
Derivatives Of

Biguanides [HN=C(NR1R2)-NH-C(NR3R4)=NH] constitute an important family of molecules used as drugs in the treatment of diabetes. When R1=R2=R3=R4=H the molecule is named simply “biguanide”. The five nitrogen atoms are potential coordination sites. Several experimental works published in literature show that in complex state, therapeutic properties of the active molecules increase considerably. In fact, the chlorine atom, a preferred substitute in pharmacy, improves the effectiveness of these drugs by increasing their activities and also by reducing their side effects. Recent experiments with Zinc complexes on diabetic animals have been very successful. In the present work a theoretical study of the coordination of N-chlorine derivatives of N-deprotonated tautomer of biguanide has been carried out. The aim is to determine, among the five nitrogen and chlorine atoms, the site most favorable to the coordination of these ligands. This determination is based on some coordination indicators. The calculations were performed by the DFT / B3LYP method in the 6-31G (d, p) orbital basis set with the Gaussian 09 and Gaussian 03 software. The DCENT-QSAR program was also used. The results of the various calculations revealed the imine nitrogen atoms as the most favorable coordination sites in the studied N-chlorosubstituted derivatives of N-deprotonated tautomeric biguanide. Complexes of these ligands with Zn (II) were modelled. The chlorine atom proved unfavorable to coordination.

scholarly journals Theoretical Atomic Radii of Elements (H-Cm): A Non-Relativistic Study with Gaussian Basis Set Using HF, Post-HF and DFT Methods

2021 ◽  
Author(s):  
Krishnamohan Prasanna ◽  
Sooraj Sunil ◽  
Ajith Kumar ◽  
Jamesh Joseph
Keyword(s):  
Electron Correlation ◽  
Van Der Waals ◽  
Basis Set ◽  
Dft Methods ◽  
Ionization Energies ◽  
Spin Polarized ◽  
Gaussian Basis Set ◽  
Van Der Waals Radii ◽  
Atomic Radii ◽  
Good Agreement

<div><p>We calculated the most probable radius of an atom for elements from H to Cm. The calculations were carried out by using non-relativistic, spin polarized, HF, MP2 and DFT methods with all electron Gaussian basis set<i>. </i>Periodicity of atomic radii was correlated with the experimental first ionization energies. This non-relativistic atomic radii were also compared with other theoretical atomic radii. With respect to the Dirac-Slater data, our values were in good agreement with the elements up to Sn. Relationship with van der Waals radii of noble gases was discussed. Anomalous properties of Gd and Pd were examined. Linearity of lanthanide contraction of elements with <i>4f </i>electrons is illustrated. This linearity is found independent of the extent of electron correlation. S.I. give data of calculated radii and other correlated studies (with ionization energies, another theoretical radii etc.)</p></div>

scholarly journals Theoretical Atomic Radii of Elements (H-Cm): A Non-Relativistic Study with Gaussian Basis Set Using HF, Post-HF and DFT Methods

2021 ◽  
Author(s):  
Krishnamohan Prasanna ◽  
Sooraj Sunil ◽  
Ajith Kumar ◽  
Jamesh Joseph
Keyword(s):  
Electron Correlation ◽  
Van Der Waals ◽  
Basis Set ◽  
Dft Methods ◽  
Ionization Energies ◽  
Spin Polarized ◽  
Gaussian Basis Set ◽  
Van Der Waals Radii ◽  
Atomic Radii ◽  
Good Agreement

<div><p>We calculated the most probable radius of an atom for elements from H to Cm. The calculations were carried out by using non-relativistic, spin polarized, HF, MP2 and DFT methods with all electron Gaussian basis set<i>. </i>Periodicity of atomic radii was correlated with the experimental first ionization energies. This non-relativistic atomic radii were also compared with other theoretical atomic radii. With respect to the Dirac-Slater data, our values were in good agreement with the elements up to Sn. Relationship with van der Waals radii of noble gases was discussed. Anomalous properties of Gd and Pd were examined. Linearity of lanthanide contraction of elements with <i>4f </i>electrons is illustrated. This linearity is found independent of the extent of electron correlation. S.I. give data of calculated radii and other correlated studies (with ionization energies, another theoretical radii etc.)</p></div>

scholarly journals Spectroscopic and Theoretical Study of the Intramolecular π-Type Hydrogen Bonding and Conformations of 2-Cyclopenten-1-ol

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1106
Author(s):  
Esther J. Ocola ◽  
Jaan Laane
Keyword(s):  
Hydrogen Bonding ◽  
Internal Rotation ◽  
Energy Surface ◽  
Theoretical Study ◽  
Conformational Dynamics ◽  
The Other ◽  
Basis Set ◽  
Ring Puckering ◽  
High Level ◽  
Calculated Distance

The conformations of 2-cyclopenten-1-ol (2CPOL) have been investigated by high-level theoretical computations and infrared spectroscopy. The six conformational minima correspond to specific values of the ring-puckering and OH internal rotation coordinates. The conformation with the lowest energy possesses intramolecular π-type hydrogen bonding. A second conformer with weaker hydrogen bonding has somewhat higher energy. Ab initio coupled-cluster theory with single and double excitations (CCSD) was used with the cc-pVTZ (triple-ζ) basis set to calculate the two-dimensional potential energy surface (PES) governing the conformational dynamics along the ring-puckering and internal rotation coordinates. The two conformers with the hydrogen bonding lie about 300 cm−1 (0.8 kcal/mole) lower in energy than the other four conformers. The lowest energy conformation has a calculated distance of 2.68 Å from the hydrogen atom on the OH group to the middle of the C=C double bond. For the other conformers, this distance is at least 0.3 Å longer. The infrared spectrum in the O-H stretching region agrees well with the predicted frequency differences between the conformers and shows the conformers with the hydrogen bonding to have the lowest values. The infrared spectra in other regions arise mostly from the two hydrogen-bonded species.

scholarly journals Crystal structure and DFT computational studies of (E)-2,4-di-tert-butyl-6-{[3-(trifluoromethyl)benzyl]iminomethyl}phenol

2020 ◽  
Vol 76 (5) ◽  
pp. 732-735
Author(s):  
Nihal Kan Kaynar ◽  
Hasan Tanak ◽  
Mustafa Macit ◽  
Namık Özdemir
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Density Functional ◽  
Basis Set ◽  
Aromatic Rings ◽  
Dft Methods ◽  
Functional Theory ◽  
Compound C ◽  
Potential Map ◽  
Good Agreement

The title compound, C23H28F3NO, is an ortho-hydroxy Schiff base compound, which adopts the enol–imine tautomeric form in the solid state. The molecular structure is not planar and the dihedral angle between the planes of the aromatic rings is 85.52 (10)°. The trifluoromethyl group shows rotational disorder over two sites, with occupancies of 0.798 (6) and 0.202 (6). An intramolecular O—H...N hydrogen bonding generates an S(6) ring motif. The crystal structure is consolidated by C—H...π interactions. The molecular structure was optimized via density functional theory (DFT) methods with the B3LYP functional and LanL2DZ basis set. The theoretical structure is in good agreement with the experimental data. The frontier orbitals and molecular electrostatic potential map were also examined by DFT computations.

scholarly journals A theoretical study on the regio- and stereoselectivity of [3+2] cycloaddition of 2-(trifluoroacetyl)vinyl ethyl ether to 2-arylidene-5-oxopyrazolidin-2-ium-1-ides

2018 ◽  
Vol 83 (3) ◽  
pp. 285-303
Author(s):  
Mina Haghdadi ◽  
Nasim Nab
Keyword(s):  
Gas Phase ◽  
Ethyl Ether ◽  
Density Functional ◽  
Theoretical Study ◽  
Reaction Pathways ◽  
Dft Methods ◽  
Functional Theory ◽  
Remarkable Effect ◽  
Phase Selectivity ◽  
Good Agreement

[3+2] Cycloaddition reactions of 2-(trifluoroacetyl)vinyl ethyl ether (1) to substituted and unsubstitued 2-arylidene-5-oxopyrazolidin-2-ium-1-ides (2a?e) were studied using density functional theory (DFT) methods at the cc-pVDZ level. The mechanistic details of these reactions, especially with respect to regio- and stereoselectivity, were analyzed. Analysis of the relative energies that are associated with the different reaction pathways indicated that the presence of the trifluoroacetyl group in the dipolarophile and substituents on the aryl ring in the dipolar have a remarkable effect on selectivity. In addition, it was found that the ortho?endo pathway with the lowest activation energy is preferred, which is in good agreement with the experimental data. Moreover, the elimination of ethanol from the [3+2] cycloadducts and the formation of bicyclic pyrazolidinones are explained in order to give a total description of the complete domino processes. The inclusion of solvent effects increased the activation energies and the exothermic character of the cycloadducts, but did not change the gas phase selectivity. The DFT-based reactivity indices clearly predicted the experimental regiochemistry.

scholarly journals Estudo cinético da abstração do hidrogênio do acetato de metila

2020 ◽  
Author(s):  
Leandro da Silva Pereira ◽  
Leonardo Baptista
Keyword(s):  
Transition State Theory ◽  
Methyl Esters ◽  
Hydrogen Abstraction ◽  
State Theory ◽  
Basis Set ◽  
Rate Coefficients ◽  
Dft Methods ◽  
Carbon Chains ◽  
Kinetics Of ◽  
Good Agreement

Biodiesel is a fuel formed by methyl esters with large carbon chains. The investigation of the hydrogen abstraction reactions of small methyl esters can be helpful to the improvement and development of kinetics models of biodiesel combustion. For this reason, the present study aims to study the thermochemistry and kinetics of hydrogen abstraction of methyl ethanoate using DFT methods and transition state theory. The abstraction reactions by O2, O, HO2, and H were studied with the B3LYP-D3 and M06-2X functionals with cc-pVDZ, ccpVTZ, aug-cc-pVDZ, and aug-cc-pVTZ basis set. At 298 K, the rate coefficients evaluated are in good agreement with the literature’s coefficients and the faster reaction occurs in the presence of O atoms. The hydrogen abstraction by O2 molecule it is not important at 298 K, but should be included in the present study since it should be important at higher temperatures.

Theoretical study of the 1,3-DC reaction between fluorinated alkynes and azides: Reactivity indices, transition structures, IGM and ELF analysis

2020 ◽  
Vol 94 ◽  
pp. 107458 ◽  
Author(s):  
Mohammed Salah ◽  
Abdellah Zeroual ◽  
Souad Jorio ◽  
Hamza El hadki ◽  
Oum Keltoum Kabbaj ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Reactivity Indices ◽  
Transition Structures
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