Tautomerism of pyrimidine bases?uracil, cytosine, isocytosine: Theoretical study with complete optimization of geometry

1979 ◽  
Vol 16 (3) ◽  
pp. 605-613 ◽  
Author(s):  
R. Czermi?ski ◽  
B. Lesyng ◽  
A. Pohorille
Keyword(s):  
Theoretical Study ◽  
Optimization Of Geometry ◽  
Pyrimidine Bases ◽  
Complete Optimization

A Theoretical Study of Fulvene Radical Anions

1991 ◽  
Vol 46 (3) ◽  
pp. 247-255 ◽  
Author(s):  
Salim M. Khalil ◽  
Hayfa M. Jarjis
Keyword(s):  
Theoretical Study ◽  
Dipole Moments ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Radical Anions ◽  
Optimization Of Geometry ◽  
Stabilization Effect ◽  
Complete Optimization ◽  
Spin Densities

AbstractMINDO-Forces calculations have been performed, with complete optimization of geometry on fulvene and X-fulvene radical anions, where X is OH, NH2, CH3, NO,2 CN, F, dimethyl and cyclopropyl. A twisted structure with angle 5° was found for fulvene anion. All substituents are stabilizing. The stabilization effect is more pronounced in the case of NO2, and very weak in the case of CH3. It was found that the substituents CH3 and CN show amphielectronic behaviour. Geometrical parameters, heats of formation, dipole moments, electron and spin densities are reported

A Theoretical Study of Monosubstituted Fulvenes

1990 ◽  
Vol 45 (6) ◽  
pp. 799-806 ◽  
Author(s):  
Hayfa M. Jarjis ◽  
Salim M. Khalil
Keyword(s):  
Dipole Moment ◽  
Double Bond ◽  
Theoretical Study ◽  
Heats Of Formation ◽  
Exocyclic Double Bond ◽  
Geometrical Parameters ◽  
Electron Densities ◽  
Orbital Energies ◽  
Optimization Of Geometry ◽  
Complete Optimization

AbstractMINDO-forces calculations have been done after complete optimization of geometry on X-monosubstituted fulvenes, where X is OH, NH2 , CH3, NO2, CN, F, dimethyl and cyclopropyl. It was found that all the substituents are stabilizing. The electron releasing substituents increase the dipole moment at the exocyclic double bond while the electron withdrawing ones increase the dipole moment at the endocyclic diene. Geometrical parameters, heats of formation, orbital energies and electron densities are reported.

A Theoretical Study of Monosubstituted Cyclopropenyl System

1992 ◽  
Vol 47 (6) ◽  
pp. 768-774 ◽  
Author(s):  
Noha M. Yahya ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Study ◽  
Membered Ring ◽  
Planar Structure ◽  
Ring Plane ◽  
Pyramidal Structure ◽  
Bond Angles ◽  
Optimization Of Geometry ◽  
The Stability ◽  
Electron Demand ◽  
Complete Optimization

AbstractMONDO-Forces calculations have been performed, with complete optimization of geometry on X-cyclopropenyl system (cations, radicals and anions), where X is H, O-, OH, CH3 , CN, NO2 , F and CF3 . All substituents prefer planar structure when substituted on both cations and radicals, while they prefer pyramidal structure in the case of anions except CF3 . The substituents O-, OH and F act as electron releasing, while CHO, NO2 and CF3 act as electron withdrawing when substituted on cyclopropenyl system. CH3 and CN show amphielectronic behaviour. They act as electron releasing on the cations and withdrawing on both radicals and anions depending on electron demand. In the case of cations and radicals, all substituents were found to increase the vicinal bonds and decrease the distal bonds and bond angles to which the substituent is attached. For anions the substitutents show no such regularity because the substituents are out of the three-membered ring plane. All substituents increase the stability of the cyclopropenyl system except CF3 in the case of the cation.

A Theoretical Study of Fulvene Radical Cations

1988 ◽  
Vol 43 (5) ◽  
pp. 485-493
Author(s):  
Salim M. Khalil
Keyword(s):  
Radical Cation ◽  
Theoretical Study ◽  
Dipole Moments ◽  
Radical Cations ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Electron Densities ◽  
Optimization Of Geometry ◽  
Complete Optimization

MINDO-Forces calculations have been performed, after complete optimization of geometry, on fulvene molecule, fulvene and X-fulvene radical cations, where X is OH, NH2, CH3, NO2, CN and F. A twisted structure with angle 5° was found for fulvene radical cation. The substituents OH, NH2, CH3, CN and F are stabilizing. NO2 is slightly stabilizing. Geometrical parameters, heats of formation, dipole moments and electron densities are reported.

A Theoretical Study of Substituted Stepwise Fluorinated Cyclopropanone Keto-Enol System

2003 ◽  
Vol 58 (12) ◽  
pp. 749-755
Author(s):  
Abdullah El-Alali ◽  
Ali A. Marashdeh ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Study ◽  
Dipole Moments ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Isodesmic Reactions ◽  
Orbital Energies ◽  
Substantial Concentration ◽  
Homo Lumo ◽  
Complete Optimization

MINDO-Forces calculations have been performed with complete optimization of the geometries on stepwise fluorinated cyclopropanones and their enols. Increase in the number of fluorine atoms causes destabilization of cyclopropanone. Perfluorinated enol was found to be present in substantial concentration, as was mentioned in previous work. This is supported by calculations of Gibbs free energies and isodesmic reactions. Geometrical parameters, heats of formation, electron densities, dipole moments and orbital energies (HOMO-LUMO) are reported.

MINDO-Forces Calculations of 1-Substituted Cyclopropyl Cations and Anions

1988 ◽  
Vol 43 (8-9) ◽  
pp. 801-805 ◽  
Author(s):  
Salim M. Khalil
Keyword(s):  
Optimization Of Geometry ◽  
Electron Demand ◽  
Complete Optimization

AbstractMINDO-Forces calculations are reported, after complete optimization of geometry, for 1-X-sub- stituted cyclopropyl cations and anions, where X is H, O-, OH, NH2, CH3, NO2, CN, F, CHO. All the substituents are stabilizing. It was found that the π-donating groups interact strongly with the cyclopropyl cations, whereas the π-withdrawing groups interact strongly with cyclopropyl anion depending on the electron demand.

A Theoretical Study of α-CFnH3-n -substituted Cyclopropyl Cations

1990 ◽  
Vol 45 (5) ◽  
pp. 730-732 ◽  
Author(s):  
Salim M. Khalil ◽  
Hayfa M. Jarjis
Keyword(s):  
Carbon Atom ◽  
Fluorine Atom ◽  
Theoretical Study ◽  
Type Orbital ◽  
Complete Optimization

Abstract MINDO-forces calculations are performed, with complete optimization of geometries, on α-Xcyclopropylcations, where X is CF3 , CF2H, and CFH2. It was found that the fluorine atom interacts with the localized empty Pπ-type orbital on α-carbon atom and forms a bridge with an angle 57.1 degree. Calculations also are performed on CF3-cyclopropyl anion and CF2H-cyclopropenyl cation. The fluorine atom in CF3 and CF2H shows no such interaction with the a-carbon atom because there is no localized empty Prc-type orbital

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