MINDO – Forces Calculation of Some Substituted Phenylallyl Cations

2004 ◽  
Vol 59 (12) ◽  
pp. 971-976
Author(s):  
Salim Y. Hanna ◽  
Salim M. Khalil ◽  
Moafaq Y. Shandala
Keyword(s):  
Correlation Analysis ◽  
Electron Density ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Molecular Orbital Calculations ◽  
Electron Densities ◽  
Stabilization Energies ◽  
Complete Geometry Optimization

MINDO-Forces SCF-molecular orbital calculations with complete geometry optimization have been performed on x-substituted phenylallyl cations, where x is H, OCH3, NH2, NO2, CN, F and CH3, in ortho, meta, or para positions. Optimized geometrical parameters, electron densities, heats of formation and stabilization energies were obtained. The substitutent effect on the geometrical parameters and the electron density are discussed by correlation analysis.

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.

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.

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.

MINDO-Forces Study on the Substituent Effect in the Keto-Enol Tautomerism of Acetyl Derivatives

2004 ◽  
Vol 59 (4-5) ◽  
pp. 299-308
Author(s):  
Wasim F. Al-Halasah ◽  
Ali Mahasnah ◽  
Salim M. Khalil
Keyword(s):  
Vinyl Alcohol ◽  
Substituent Effect ◽  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Orbital Energies ◽  
Homo Lumo ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on acetaldehyde, vinyl alcohol and acetyl derivatives CH3COX(X=H, F, OH, CN, NH2, NO2 , CH3 , CF3,OCH3). It was found that acetaldehyde is more stable than vinyl alcohol by 10.451 kcal/mol. Thermodynamically, keto tautomers are more stable than their enol counterparts. This agrees with theoretical calculations. The electron releasing substituents tend to stabilize keto tautomers, while the electron withdrawing substituents tend to destabilize the keto tautomers, relative to the parent. Geometrical parameters, heats of formation, electron densities, Gibbs free energies and orbital energies (HOMO-LUMO) are reported.

Molecular orbital structures of sulfones

1982 ◽  
Vol 60 (6) ◽  
pp. 730-734 ◽  
Author(s):  
Russell J. Boyd ◽  
Jeffrey P. Szabo
Keyword(s):  
Crystal Structure ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Membered Ring ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
Comparison With Experiment ◽  
The Difference

Abinitio molecular orbital calculations are reported for several cyclic and acyclic sulfones. The geometries of XSO2Y, where X, Y = H, F, or CH3 are optimized at the STO-3G* level. Similar calculations are reported for the smallest cyclic sulfone, thiirane-1,1 -dioxide, as well as the corresponding sulfoxide, thiirane-1-oxide, and the parent sulfide, thiirane. Where comparison with experiment is possible, the agreement is satisfactory. In order to consider the possibility of substantial differences between axial and equatorial S—O bonds in the gas phase, as observed in the crystal structure of 5H,8H-dibenzo[d,f][1,2]-dithiocin-1,1-dioxide, STO-3G* calculations are reported for a six-membered ring, thiane-1,1-dioxide, and a model eight-membered ring. Limited geometry optimization of the axial and equatorial S—O bonds in the chair conformations of the six- and eight-membered rings leads to bond lengths of 1.46 Å with the difference being less than 0.01 Å.

The stabilization of alkoxide anions

1969 ◽  
Vol 47 (12) ◽  
pp. 2306-2307 ◽  
Author(s):  
N. C. Baird
Keyword(s):  
Electron Density ◽  
Molecular Orbital ◽  
Cyclotron Resonance ◽  
Molecular Orbital Calculations ◽  
Ion Cyclotron Resonance ◽  
Density Distributions ◽  
Alkyl Groups ◽  
Valence Electrons ◽  
Ion Cyclotron

Molecular orbital calculations by the MINDO method are reported for the valence electrons of HO− and a number of small alkoxide anions. The acidity order [Formula: see text] is predicted, in agreement with recent ion cyclotron resonance studies. The electron density distributions within the ions are discussed with reference to current models of the polarizability of alkyl groups.

Molecular Mimicry of Structure and Electron Density Distributions in Minerals

1986 ◽  
Vol 73 ◽  
Author(s):  
G. V. Gibbs ◽  
M. B. Boisen
Keyword(s):  
Bond Strength ◽  
Electron Density ◽  
Molecular Orbital ◽  
Computational Models ◽  
Molecular Mimicry ◽  
Strength Parameter ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
Density Distributions ◽  
Reaction Energies

ABSTRACTMolecular orbital calculations on hydroxyacid molecules with first- and secondrow X-cations (X = Li through N and Na through S) yield bond lengths and angles that mimic those of chemically similar minerals. These bond lengths are used to find a formula giving bond length as a function of a bond-strength parameter that reproduces XO bond lengths in crystals with main-group X-cations from all six rows of the periodic table within 0.05Å on average. The molecular orbital calculations also provide insights into reaction energies, physical properties of crystals such as electron density distributions, and data not amenable to direct measurement. They also provide a basis from which computational models for mineral structures may be constructed.

An investigation into the origins of polar substituent effects upon 19F chemical shifts, using 4-substituted β,β-difluorostyrenes

1980 ◽  
Vol 58 (8) ◽  
pp. 839-845 ◽  
Author(s):  
William F. Reynolds ◽  
Victoria G. Gibb ◽  
Nick Plavac
Keyword(s):  
Chemical Shift ◽  
Electron Density ◽  
Molecular Orbital ◽  
Excellent Agreement ◽  
Field Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Molecular Orbital Calculations ◽  
Chemical Shift Difference ◽  
Polar Substituent

19F, 13C, and 1H chemical shifts have been determined for β,β-difluorostyrene and eight 4-substituted derivatives. The β-fluorine chemical shift difference, ΔδF, is used to evaluate the constant in the Buckingham equation. A = 3.0 × 10−11 esu for C—F bonds which is in excellent agreement with the value derived by Adcock and Khor. This allows accurate estimates of direct field effect contributions to 19F chemical shifts in aryl fluorides. Substituent parameter correlations demonstrate that the primary polar effect on 19F chemical shifts is field-induced π polarization. Abinitio molecular orbital calculations confirm that the substituent-induced 19F chemical shifts reflect changes in fluorine π electron density.

Asymmetric induction in Diels–Alder reactions of α-alkoxyorthoquinodimethanes

1989 ◽  
Vol 67 (6) ◽  
pp. 1010-1014 ◽  
Author(s):  
James L. Charlton ◽  
Guy L. Plourde ◽  
Glenn H. Penner
Keyword(s):  
Molecular Orbital ◽  
Geometry Optimization ◽  
Diels Alder ◽  
Asymmetric Induction ◽  
Molecular Orbital Calculations ◽  
Cycloaddition Reactions ◽  
Vinyl Ethers ◽  
The Face ◽  
Face Selectivity ◽  
Alkoxy Groups

It has been shown that dienophiles cycloadd selectively to one face of o-quinodimethanes (o-QDMs) bearing chiral α-alkoxy groups. The face selectivity (diastereoselectivity) increases for the series of chiral groups -OCH(Ph)CH3, -OCH(Ph)CH(CH3)2, and -OCH(Ph)C(CH3)3. A similar effect on the face selectivity of the Diels–Alder reactions of chiral alkoxy vinyl ethers for the same series of chiral groups has been noted previously by others. A mechanism has been proposed to explain the face selectivity in the cycloaddition reactions of the alkoxy o-QDMs. Abinitio molecular orbital calculations with geometry optimization on vinyl 1-phenylethyl ether to determine its lowest energy conformations support the proposed mechanism. The absolute stereochemistries of the o-QDM cycloadducts have been determined to verify the predictions of the model. Keywords: o-quinodimethanes, asymmetric, Diels–Alder, cycloaddition.

Sulfonyl radicals, sulfinic acid, and related species: an abinitio molecular orbital study

1980 ◽  
Vol 58 (4) ◽  
pp. 331-338 ◽  
Author(s):  
Russell J. Boyd ◽  
Abha Gupta ◽  
Richard F. Langler ◽  
Stephen P. Lownie ◽  
James A. Pincock
Keyword(s):  
Molecular Orbital ◽  
Functional Group ◽  
Basis Set ◽  
Geometrical Parameters ◽  
Molecular Orbital Calculations ◽  
Sulfinic Acid ◽  
Molecular Orbital Study ◽  
Polarization Functions ◽  
Total Energies ◽  
D Orbitals

Extensive abinitio molecular orbital calculations on six sulfonyl radicals (XSO2 where X = H, CH3, NH2, OH, F, and Cl), the simplest sulfinic acid HSO2H3 and its isomeric sulfone H2SO2, the HSO2− anion of sulfinic acid, the isomeric anion SO2H−, and for completeness, the SO2H radical are presented. By use of the STO-3G* basis set, which includes d-type polarization functions on second-row atoms, all geometrical parameters are varied until the total energy is minimized, subject only to certain symmetry restrictions specified for each system. The inclusion of d orbitals on S is observed to affect the S—O bond lengths by as much as 0.45 Å. The calculations suggest that the radical site in sulfonyl radicals is significantly delocalized over the entire functional group and that the geometrical parameters of the SO2 functional group in sulfonyl radicals are nearly independent of the substituent (r(S—O) = 1.47 ± 0.01 Å, < OSO = 123 ± 2°). Estimates of the X—S bond energy in CH3SO2, NH2SO2, and OHSO2 are consistent with the chemistry of alkylsulfonyl and aminosulfonyl radicals and lead to an interesting prediction for alkoxylsulfonyl radicals. Furthermore the calculations yield lower total energies for HSO2H, HSO2−, and SO2H than for the respective isomeric forms H2SO2, SO2H−, and HSO2.

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