scholarly journals A Theoretical Study of Substituted Cyclobutanones and Their Enols

2004 ◽  
Vol 59 (11) ◽  
pp. 838-844
Author(s):  
Mohammad I. Sway ◽  
Iyad D. Al-Shawabkeh ◽  
Salim M. Khalil
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Theoretical Study ◽  
Theoretical Calculations ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Electron Densities ◽  
Complete Optimization ◽  
Electron Withdrawing Substituents

MINDO-Forces calculations have been performed with complete optimization of the geometry on cyclobutanone and its enol counterpart, perfluorination of cyclobutanones and enol counterparts, and X-cycolobutanones and their X-enols, where X is NO2, CF3, CN, OH, NH2 and F. It was found that ketone is more stable than its enol counterpart. Perfluorination destabilizes ketone on the expense of enol. These results agree with experimental and theoretical calculations. Electron releasing substituents (NH2, OH, F) stabilize cyclobutanone, while electron withdrawing substituents (CF3, NO2) destabilize it. CN substituents have almost no effect on the stabilization of this keto-enol system. Geometrical parameters, heats of formation, electron densities and Gibbs free energy 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.

Theoretical Study of the Effect of Different α-Substituents on the Acetaldimine-Vinylamine Tautomeric System

2004 ◽  
Vol 59 (6) ◽  
pp. 382-388
Author(s):  
Hamzeh S. M. Al-Omari
Keyword(s):  
Free Energy ◽  
Proton Transfer ◽  
Gibbs Free Energy ◽  
Theoretical Study ◽  
Semiempirical Method ◽  
Heats Of Formation ◽  
Geometrical Parameters

The Acetaldimine-Vinylamine tautomeric system has been studied by employing the MNDO semiempirical method. The imine structure was found to be energetically favorable, as indicated by the calculated heats of formation, Gibbs free energy, LUMO and HOMO, and charges. The substitution of F, Cl, CN, CH3, CF3, NO2 and BH2 at the α-position was found to affect the geometrical parameters. F and Cl substituents are found to favor the imine formation, while CF3, NO2, CN2 and BH2 favor the amine formation. The proton transfer in this tautomeric system is found to be easier (ΔH = 5.224 kcal/mol) than that in the keto-enol tautomeric system (ΔH = 11.1 kcal/mol).

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 Study on Substituted Nitromethane ⇋ aci-Nitromethane Tautomerism

2005 ◽  
Vol 60 (1-2) ◽  
pp. 47-53
Author(s):  
Bareehan M. Salim ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Electron Densities ◽  
Isodesmic Reactions ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on nitromethane, aci-nitromethane and X-substituted nitromethane and aci-nitromethane (X = F, OH, NH2, CH3, CN, CF3, NO2, CHO). It is found that nitromethane is more stable than aci-nitromethane by 9.337 kcal/mol. This agrees with theoretical calculations. Thermodynamically, substituted aci-nitro tautomers are more stable than the corresponding nitromethane, except in case of the substituent F. Geometrical parameters, heats of formation, electron densities, Gibbs free energies and isodesmic reactions are reported.

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

Effect of Different Substituents on Uracil and its 2-Hydroxy-4-oxo Enol Tautomer – A Theoretical Study

2008 ◽  
Vol 63 (10-11) ◽  
pp. 693-702
Author(s):  
Hamzeh S. M. Al-Omari
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Theoretical Study ◽  
Equilibrium Constants ◽  
Semiempirical Method ◽  
Forward Direction ◽  
Heat Of Formation ◽  
Geometrical Parameters ◽  
Homo And Lumo ◽  
Enol Tautomer

The uracil/2-hydroxy-4-oxo uracil tautomeric system was studied by employing the MNDO semiempirical method for the calculations. The uracil structure was found to be energetically favourable as indicated by the calculated heat of formation, the Gibbs free energy, the HOMO and LUMO energies, and charges. The substitution by F, OH, NH2, CH3, and BH2 at the carbon-6 position was found to affect the geometrical parameters of the substituted molecules. All of the substituents were found to shift the equilibrium in forward direction compared to the unsubstituted tautomeric pair as indicated by the calculated values for the equilibrium constants.

scholarly journals Detection of Chemical Weapon Agents Using Spectroscopic Probes: A Computational Study

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Letícia S. Braga ◽  
Érika F. Silva ◽  
Daiana T. Mancini ◽  
Eduardo P. da Rocha ◽  
Elaine F. F. da Cunha ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Organophosphorus Compounds ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Spectroscopic Properties ◽  
Acetylcholinesterase Inhibition ◽  
Chemical Weapon ◽  
Fast Detection ◽  
Absorption Wavelength

Organophosphorus compounds are organic compounds widely employed in agriculture as well as in chemical weapons. The use in agriculture is due to their insecticidal properties. However, in chemical warfare, the use of organophosphorus is associated with acetylcholinesterase inhibition, which promotes the cholinergic syndromes. In this line, the fast detection of this class of compound is crucial for the determination of environmental exposure. This improved detection will naturally allow for more prompt courses of treatment depending on the contaminant findings. In this perspective, the dipyrrinone oxime (1) was employed for the detection of organophosphorus compounds that are employed as nerve agents, such as cyclosarin, sarin, soman, diethyl chlorophosphate, diisopropylfluorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, O-ethyl-S-[2-(diethylamino)ethyl]methylphosphonothioate, O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate, through fluorescent emission. The thermodynamics and kinetic parameters as well as spectroscopic properties of the complexes formed for 1 and all organophosphorus compounds previously cited were investigated by means of theoretical calculations. From our findings, only the diethyl chlorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate emitted fluorescence in the hexane, toluene, chloroform, dichloromethane, methanol, acetonitrile, water, and dimethyl sulfoxide solvents. The study of the absorption wavelength with the most polar solvent showed higher values compared to apolar solvents. In the same solvent, for instance, soman in hexane showed the lowest absorption wavelength value, 324.5 nm, and DCP the highest value, 330.8 nm. This behavior was observed in other tested solvents. The thermodynamic parameters indicate negative Gibbs free energy (ΔG) values for the O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate with 1 reaction. On the other hand, the sarin and cyclosarin revealed the lowest Gibbs free energy (ΔG‡) values, being kinetically favorable and presenting more reactivity.

Mindo-Forces Study on the Keto-Enol Tautomerism of α-Substituted Acetaldehydes XCH2CH=O (X = H, F, Oh, Cn, NH2, NO2, CH3, CF3, OCH3): Comparison with Acetyl Derivatives

2004 ◽  
Vol 59 (12) ◽  
pp. 980-986
Author(s):  
Wasim F. Al-Halasah ◽  
Salim M. Khalil
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Substituent Effects ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Electron Densities ◽  
The Stability ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on α- substituted acetaldehydes XCH2CH=O and their enols (X = H, F, OH, CN, NH2, NO2, CH3, CF3, OCH3). All substituents were found to decrease the stability of the acetaldehyde and mostly in the case of electron withdrawing capacity (e. g NO2 and CF3). This agrees with theoretical calculations, except in the case of F. The substituent effects on the stabilities in this study are compared with results obtained from our previous theoretical calculations on acetyl derivatives. Geometrical parameters, electron densities, and Gibbs free energies are reported.

Substitutent Effects on the Geometrical Properties of 1-Phenylallyl Alcohol

2005 ◽  
Vol 60 (4) ◽  
pp. 265-270
Author(s):  
Salim Y. Hanna ◽  
Salim M. Khalil ◽  
Moafaq Y. Shandala
Keyword(s):  
Electron Density ◽  
Molecular Orbital ◽  
Substituent Effects ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Molecular Orbital Calculations ◽  
Electron Densities ◽  
Geometrical Properties ◽  
Stabilization Energies

Abstract Optimized geometrical parameters, electron densities, heats of formation and stabilization energies have been obtained on X-substituted phenylallyl alcohols, where X is H, OCH3, NH2, CN, F and CH3 at ortho, meta, and para positions, using MINDO-Forces SCF-molecular orbital calculations. The substituent effects on the geometrical parameters and the electron density are discussed.

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