scholarly journals Does the Intramolecular Hydrogen Bond Affect the Spectroscopic Properties of Bicyclic Diazole Heterocycles?

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Paweł Misiak ◽  
Alina T. Dubis ◽  
Andrzej Łapiński
Keyword(s):  
Hydrogen Bond ◽  
Quantum Theory ◽  
Intramolecular Hydrogen Bond ◽  
Natural Bond Orbital ◽  
Spectroscopic Properties ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Nbo Method ◽  
Acceptor Group ◽  
Intramolecular Hydrogen

The formation of an intramolecular hydrogen bond in pyrrolo[1,2-a]pyrazin-1(2H)-one bicyclic diazoles was analyzed, and the influence of N-substitution on HB formation is discussed in this study. B3LYP/aug-cc-pVDZ calculations were performed for the diazole, and the quantum theory of atoms in molecules (QTAIM) approach as well as the natural bond orbital (NBO) method was applied to analyze the strength of this interaction. It was found that the intramolecular hydrogen bond that closes an extra ring between the C=O proton acceptor group and the CH proton donor, that is, C=O⋯H–C, influences the spectroscopic properties of pyrrolopyrazine bicyclic diazoles, particularly the carbonyl frequencies. The influence of N-substitution on the aromaticity of heterocyclic rings is also discussed in this report.

scholarly journals Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

2012 ◽  
Vol 8 ◽  
pp. 112-117 ◽  
Author(s):  
Tânia A O Fonseca ◽  
Matheus P Freitas ◽  
Rodrigo A Cormanich ◽  
Teodorico C Ramalho ◽  
Cláudio F Tormena ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Quantum Theory ◽  
Intramolecular Hydrogen Bond ◽  
Natural Bond Orbital ◽  
Intramolecular Hydrogen Bonding ◽  
Nbo Analysis ◽  
Conformational Isomerism ◽  
Intramolecular Hydrogen ◽  
Stereoelectronic Interactions

The conformational isomerism and stereoelectronic interactions present in 2'-haloflavonols were computationally analyzed. On the basis of the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis, the conformer stabilities of 2'-haloflavonols were found to be dictated mainly by a C=O···H–O intramolecular hydrogen bond, but an unusual C–F···H–O hydrogen-bond and intramolecular C–X···O nonbonding interactions are also present in such compounds.

Intramolecular hydrogen bonds and the orientation of amino groupsin o-phenylenediamines

1967 ◽  
Vol 45 (19) ◽  
pp. 2135-2141 ◽  
Author(s):  
P. J. Krueger
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Infrared Absorption ◽  
Substituent Effect ◽  
Proton Donor ◽  
Proton Acceptor ◽  
Amino Groups ◽  
Intramolecular Hydrogen Bonds ◽  
Infrared Absorption Spectra ◽  
Intramolecular Hydrogen

The infrared absorption spectra of partially deuterated o-phenylenediamine and 4,5-di-methyl-, 4-methyl-, and 4-chloro-o-phenylenediamine in dilute CCl4 solution show double intramolecular [Formula: see text] hydrogen bonds in which the two NHD groups are equivalent and each group acts as both a proton donor and a proton acceptor. The ring substituent effect on this interaction in these compounds is small. In 4-methoxy-o-phenylenediamine, the amino groups are not equivalent, but double intramolecular hydrogen bonds are still present. In 4-nitro-o-phenylenediamine, only one intramolecular [Formula: see text] hydrogen bond appears to exist. The effect of N-substitution on some of these observations is discussed.

Effect of substituents at the proton-donor nitrogen atom on an intramolecular hydrogen bond of type NH...O

1974 ◽  
Vol 15 (3) ◽  
pp. 353-356
Author(s):  
L. N. Kurkovaskaya ◽  
I. L. Radushnova ◽  
N. N. Shapet'ko ◽  
S. M. Kvitko ◽  
Yu. S. Andreichikov ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Nitrogen Atom ◽  
Intramolecular Hydrogen Bond ◽  
Proton Donor ◽  
Effect Of Substituents ◽  
Donor Nitrogen Atom ◽  
Donor Nitrogen ◽  
Intramolecular Hydrogen

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.

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