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.

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.

Molecular and Crystal Structures of Cubane-like Ru−O Complexes and the Molecular Orbital Analysis of an Unusual π−π Interaction Stabilized by C−H···O Hydrogen Bonds

2000 ◽  
Vol 19 (5) ◽  
pp. 790-797 ◽  
Author(s):  
Laura Scaccianoce ◽  
Dario Braga ◽  
Maria José Calhorda ◽  
Fabrizia Grepioni ◽  
Brian F. G. Johnson
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Molecular Orbital ◽  
Molecular And Crystal Structures ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis

Effect of the intramolecular hydrogen bond in the active metabolite analogs of leflunomide for blocking the Plasmodium falciparum dihydroorotate dehydrogenase enzyme: QTAIM, NBO, and docking study

2020 ◽  
Vol 16 ◽  
Author(s):  
Reihaneh Heidarian ◽  
Mansoureh Zahedi-Tabrizi
Keyword(s):  
Hydrogen Bond ◽  
Plasmodium Falciparum ◽  
Molecular Orbital ◽  
Intramolecular Hydrogen Bond ◽  
Active Metabolite ◽  
Chemical Hardness ◽  
Dihydroorotate Dehydrogenase ◽  
Molecular Orbital Analysis ◽  
Intramolecular Hydrogen ◽  
Orbital Analysis

: Leflunomide (LFM) and its active metabolite, teriflunomide (TFM), have drawn a lot of attention for their anticancer activities, treatment of rheumatoid arthritis and malaria due to their capability to inhibit dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. In this investigation, the strength of intramolecular hydrogen bond (IHB) in five analogs of TFM (ATFM) has been analyzed employing density functional theory (DFT) using B3LYP/6-311++G (d, p) level and molecular orbital analysis in the gas phase and water solution. A detailed electronic structure study has been performed using the quantum theory of atoms in molecules (QTAIM) and the hydrogen bond energies (EHB) of stable conformer obtained in the range of 76-97 kJ/mol, as a medium hydrogen bond. The effect of substitution on the IHB nature has been studied by natural bond orbital analysis (NBO). 1H NMR calculations show an upward trend in the proton chemical shift of the enolic proton in the chelated ring (14.5 to 15.7ppm) by increasing the IHB strength. All the calculations confirmed the strongest IHB in 5-F-ATFM and the weakest IHB in 2-F-ATFM. Molecular orbital analysis, including the HOMO-LUMO gap and chemical hardness, was performed to compare the reactivity of inhibitors. Finally, molecular docking analysis was carried out to identify the potency of inhibition of these compounds against PfDHODH enzyme.

UPS Study of [2,2] (2,5)Furanophane and [2,2] (2,5)Thiophenophane Evidence Regarding the Importance of Through Bond and Through Space Interactions

1978 ◽  
Vol 33 (8) ◽  
pp. 959-963 ◽  
Author(s):  
Fernando Bernardi ◽  
Andrea Bottoni ◽  
Francesco Paolo Colonna ◽  
Giuseppe Distefano ◽  
Ugo Folli ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Photoelectron Spectra ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis

The ultraviolet photoelectron spectra of [2,2](2,5)furanophane (FUPH) and [2,2](2,5)thiophenophane (THPH) have been analyzed on the basis of a perturbational molecular orbital analysis, by comparison with CNDO/2 computations and by correlating them with the spectra of related molecules. Through space and through bond interactions between the two heteroaromatic rings are shown to be important in determining the ordering of the outermost MO’s in this class of compounds.

Understanding the mechanism of the addition of organomagnesium reagents to 2-hydroxypropanal: An ab initio molecular orbital analysis

1997 ◽  
Vol 65 (5) ◽  
pp. 719-728 ◽  
Author(s):  
M�nica Oliva ◽  
Vicent S. Safont ◽  
Juan Andr�s ◽  
Raquel Castillo ◽  
Vicente Moliner
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Analysis ◽  
Orbital Analysis
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