Component analysis of the X-C-Y anomeric effect (X = O, S; Y = F, OMe, NHMe) by DFT molecular orbital calculations and natural bond orbital analysis

2006 ◽  
Vol 84 (4) ◽  
pp. 692-701 ◽  
Author(s):  
Melissa L Trapp ◽  
Jonathan K Watts ◽  
Noham Weinberg ◽  
B Mario Pinto
Keyword(s):  
Molecular Orbital ◽  
Electrostatic Interactions ◽  
Natural Bond Orbital ◽  
Component Analysis ◽  
Natural Bond Orbital Analysis ◽  
Molecular Orbital Calculations ◽  
Orbital Interaction ◽  
Anomeric Effect ◽  
Dft Molecular Orbital Calculations ◽  
Orbital Analysis

Six 2-Y-substituted oxacyclohexane and thiacyclohexane heterocycles (Y = F, OMe, NHMe) were examined using DFT molecular orbital calculations. Natural bond orbital (NBO) analysis of the total energy behaviour yielded the orbital-interaction factors contributing to the conformational equilibria. The dipole moments of the optimized systems were used to estimate the electrostatic contributions to the anomeric effect. The primary determinant of the X-C-Y anomeric effect was found to be the orbital interaction components associated with the combined endo- and exo-anomeric effects acting in concert in the axial conformers. Electrostatic interactions made a contribution to the observed conformer stabilization in all cases, but did not account for the relative magnitudes of the energy differences among conformers of homologous molecules. In the case of the methylamino substituent, accentuated steric interactions in the axial conformer precluded stabilization by the exo-anomeric interaction and consequently, the net endo/exo anomeric stabilization did not dominate the conformational equilibria.Key words: anomeric effect, component analysis, natural bond orbital analysis, electrostatic, steric, and orbital interaction effects.

The anomeric effect on the basis of natural bond orbital analysis

2013 ◽  
Vol 11 (17) ◽  
pp. 2885 ◽  
Author(s):  
Matheus P. Freitas
Keyword(s):  
Natural Bond Orbital ◽  
Natural Bond Orbital Analysis ◽  
Anomeric Effect ◽  
Orbital Analysis

scholarly journals Theoretical investigations on the HOMO–LUMO gap and global reactivity descriptor studies, natural bond orbital, and nucleus-independent chemical shifts analyses of 3-phenylbenzo[d]thiazole-2(3H)-imine and its para-substituted derivatives: Solvent and substituent effects

2020 ◽  
pp. 174751982093209
Author(s):  
Marzieh Miar ◽  
Abolfazl Shiroudi ◽  
Khalil Pourshamsian ◽  
Ahmad Reza Oliaey ◽  
Farhad Hatamjafari
Keyword(s):  
Charge Transfer ◽  
Molecular Orbital ◽  
Relative Stability ◽  
Natural Bond Orbital ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Natural Bond Orbital Analysis ◽  
Orbital Energy ◽  
Thiazole Ring ◽  
Orbital Analysis

Natural bond orbital analysis, salvation, and substituent effects of electron-releasing (–CH3, –OH) and electron-withdrawing (–Cl, –NO2, –CF3) groups at para positions on the molecular structure of synthesized 3-phenylbenzo[ d]thiazole-2(3 H)-imine and its derivatives in selected solvents (acetone, toluene, and ethanol) and in the gas phase by employing the polarizable continuum method model are studied using the M06-2x method and 6-311++G(d,p) basis set. The relative stability of the studied compounds is influenced by the possibility of intramolecular interactions between substituents and the electron donor–acceptor centers of the thiazole ring. Furthermore, atomic charges, electron density, chemical thermodynamics, energetic properties, dipole moments, and nucleus-independent chemical shifts of the studied compounds and their relative stability are considered. The dipole moment values and the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps reveal different charge-transfer possibilities within the considered molecules. Finally, natural bond orbital analysis is carried out to picture the charge transfer between the localized bonds and lone pairs.

Conformational Stabilization of 1,3-Benzodioxole:  Anomeric Effect by Natural Bond Orbital Analysis

2001 ◽  
Vol 105 (13) ◽  
pp. 3221-3225 ◽  
Author(s):  
Seongho Moon ◽  
Younghi Kwon ◽  
Jaebum Lee ◽  
Jaebum Choo
Keyword(s):  
Natural Bond Orbital ◽  
Natural Bond Orbital Analysis ◽  
Anomeric Effect ◽  
Orbital Analysis ◽  
Conformational Stabilization

Bond angle variations in XCY fragments and their relationship to the anomeric effect

1987 ◽  
Vol 65 (7) ◽  
pp. 1658-1662 ◽  
Author(s):  
B. Mario Pinto ◽  
H. Bernhard Schlegel ◽  
Saul Wolfe
Keyword(s):  
Crystal Structures ◽  
Molecular Orbital ◽  
Bond Angle ◽  
Molecular Orbital Calculations ◽  
Equatorial Orientation ◽  
Anomeric Effect ◽  
Geometrical Effect ◽  
Geometrical Effects ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis

The crystal structures of 2-substituted heterocyclohexanes containing exocyclic X and endocyclic Y exhibit systematic variations in their XCY bond angles. When X is in the more stable axial orientation, corresponding to the anomeric effect, the XCY angle is larger than tetrahedral; when X is in the equatorial orientation the XCY angle is smaller than tetrahedral. These geometrical effects are predicted by the perturbational molecular orbital analysis employed previously to account for the existence of the anomeric effect and its variation with changes in X and Y. Abinitio molecular orbital calculations, with full geometry opimization, of selected conformations of XCH2YH molecules also reproduce this geometrical effect.

Structures of four o-nitrobenzonitriles

1996 ◽  
Vol 52 (2) ◽  
pp. 344-351 ◽  
Author(s):  
D. Britton ◽  
C. J. Cramer
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Orbital ◽  
Natural Bond Orbital ◽  
Basis Set ◽  
Nucleophilic Attack ◽  
Molecular Orbital Calculations ◽  
Hartree Fock ◽  
Intramolecular Distance ◽  
Delocalization Energy ◽  
Orbital Analysis

The crystal structures of 6-methyl- (I), 6-chloro- (II) and 5-chloro-2-nitrobenzonitrile (III), as well as 2,6-dinitrobenzonitrile (IV), have been determined. (I), orthorhombic, Pbca, a = 9.969 (2), b = 14.728 (4), c = 10.179 (3) Å, T = 180 K; (II), orthorhombic, Pbca, a = 9.469 (5), b = 14.752 (7), c = 10.859 (5) Å, T = 297 K; (III), monoclinic, P21/n, a = 7.889 (2), b = 15.064 (12), c = 7.311 (4) Å, β = 118.22 (3)°, T = 189 K; (IV), orthorhombic, Pbcn, a = 13.081 (6), b = 9.027 (4), c = 6.545 (3) Å, T = 297 K. In (I)–(III) there is a short intramolecular distance [I 2.552 (4), II 2.579 (3), III 2.599 (2) Å] between one of the nitro O atoms and the adjacent nitrile C atom. These short distances plus the accompanying molecular distortions are taken as indications of incipient nucleophilic attack of the O atoms on the electrophilic nitrile C atom. Molecular orbital calculations at the Hartree–Fock level using the 6-31G* basis set support this interpretation; natural bond-orbital analysis indicates an n O1 → π*CN delocalization energy of 10–15 kJ mol−1 for (I), (II) and (III). In (III) and (IV) the molecules pack in sheets, apparently driven by two C—H...O hydrogen bonds and a CN...Cl interaction in (III) and two C—H...O and one C—H...N hydrogen bonds in (IV).

Sign in / Sign up

Export Citation Format

Share Document