scholarly journals Evaluation of the intramolecular hydrogen bond enthalpy by means of specialized quantum chemical methods

2007 ◽  
Vol 72 (2) ◽  
pp. 151-157 ◽  
Author(s):  
Alexei Pankratov ◽  
Alexei Shalabay
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Quantitative Estimation ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Intramolecular Hydrogen

By means of the MNDO/H, I-MNDO, MNDO/HB and MNDO/M methods, the values of the enthalpy of intramolecular hydrogen bond (IHB) formation for series of substances have been computed. The applicability of these methods for a semi-quantitative estimation of the IHB enthalpy in compounds with a planar quasicycle has been shown. .

scholarly journals Complexation of Cu(BF4)2 with 3-hydroxyflavone in acetonitrile: quantum chemical calculation

2018 ◽  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Phenyl Ring ◽  
Fluorine Atom ◽  
Quantum Chemical Study ◽  
Hydroxyl Group ◽  
Chemical Calculation ◽  
Intramolecular Hydrogen

In the article the results of the quantum chemical study of copper (II) solvato-complexes with acetonitrile (AN), tetrafluoroborate anion (BF4–) and 3-hydroxyflavone (flv) of the composition [Cu(AN)6]2+, [Cu(BF4)(AN)5]+, [Cu(flv)(AN)5]2+, [Cu(flv)(BF4)(AN)4]+ are presented. Calculations were done using density function theory (DFT) on the M06-2X/6-311++G(d,p) level of theory. Obtained results were interpreted in terms of complexes geometry and topology of electron density distribution using non-covalent interactions (NCI) approach. It was shown that flv molecule is a monodentate ligand in copper (II) complexes and coordinates central atom via carbonyl oxygen. Intramolecular hydrogen bond that exists in an isolated flv molecule was found to be broken upon [Cu(flv)(AN)5]2+ complex formation. In [Cu(flv)(AN)5]2+ complex, a significant rotation of phenyl ring over the planar chromone fragment was spotted as a consequence of intramolecular hydrogen bond breaking. Upon inclusion of BF4– anion to the first solvation shell of Cu2+, an intracomplex hydrogen bond was formed between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion. NCI analysis had shown that a hydrogen bond between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion is significantly stronger than intramolecular hydrogen bond in an isolated flv molecule. In addition, flexible phenyl ring of flv molecule in [Cu(flv)(BF4)(AN)4]+ complex was found to be internally stabilized by the weak van der Waals attraction between oxygen atoms of chromone ring and phenyl hydrogens. These evidences led to a conclusion that [Cu(flv)(BF4)(AN)4]+ complex is more stable, comparing to the in [Cu(flv)(AN)5]2+ complex.

OH⋯S intramolecular hydrogen bond in thiomalonaldehyde derivatives; a quantum chemical study

2011 ◽  
Vol 963 (2-3) ◽  
pp. 517-524 ◽  
Author(s):  
A. Nowroozi ◽  
H. Roohi ◽  
H. Hajiabadi ◽  
H. Raissi ◽  
E. Khalilinia ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Intramolecular Hydrogen

scholarly journals Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

2012 ◽  
Vol 8 ◽  
pp. 1227-1232 ◽  
Author(s):  
Fátima M P de Rezende ◽  
Marilua A Moreira ◽  
Rodrigo A Cormanich ◽  
Matheus P Freitas
Keyword(s):  
Hydrogen Bond ◽  
Conformational Analysis ◽  
Quantum Chemical Calculations ◽  
Intramolecular Hydrogen Bond ◽  
Quantum Chemical ◽  
Coupling Constant ◽  
Structural Stabilization ◽  
Intramolecular Hydrogen ◽  
Nmr Properties ◽  
Stereoelectronic Interactions

Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F∙∙∙HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the 1h J F,H(O) coupling constant in the syn-exo isomer is modulated by the n F→σ*OH interaction, i.e., the quantum nature of the F∙∙∙HO hydrogen bond.

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