scholarly journals Lone pair ···π interactions between water oxygens and aromatic residues: Quantum chemical studies based on high-resolution protein structures and model compounds

2009 ◽  
pp. NA-NA ◽  
Author(s):  
Alok Jain ◽  
Venkatnarayan Ramanathan ◽  
Ramasubbu Sankararamakrishnan
Keyword(s):  
High Resolution ◽  
Quantum Chemical ◽  
Protein Structures ◽  
Lone Pair ◽  
Model Compounds ◽  
Aromatic Residues ◽  
Π Interactions ◽  
Chemical Studies ◽  
Quantum Chemical Studies

High-Resolution X-ray Diffraction and ab Initio Quantum Chemical Studies of Glycoluril, a Biotin Analog

1994 ◽  
Vol 116 (15) ◽  
pp. 6494-6507 ◽  
Author(s):  
Naiyin Li ◽  
Sergio Maluendes ◽  
Robert H. Blessing ◽  
Michel Dupuis ◽  
Grant R. Moss ◽  
...  
Keyword(s):  
High Resolution ◽  
Ab Initio ◽  
Quantum Chemical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Studies ◽  
Quantum Chemical Studies

Quantum Chemical Studies of Hole Transfer in Liquid Hexane

2017 ◽  
Vol 137 (7) ◽  
pp. 435-441
Author(s):  
Masahiro Sato ◽  
Akiko Kumada ◽  
Kunihiko Hidaka ◽  
Toshiyuki Hirano ◽  
Fumitoshi Sato
Keyword(s):  
Quantum Chemical ◽  
Hole Transfer ◽  
Chemical Studies ◽  
Quantum Chemical Studies

ESR, spectroscopic, and quantum-chemical studies on the electronic structures of complexes formed by Cu(I) with radicals

1986 ◽  
Vol 22 (1) ◽  
pp. 27-33
Author(s):  
N. P. Gritsan ◽  
O. M. Usov ◽  
N. V. Shokhirev ◽  
I. V. Khmelinskii ◽  
V. F. Plyusnin ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Quantum Chemical ◽  
Chemical Studies ◽  
Quantum Chemical Studies

scholarly journals Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 497
Author(s):  
Ewa D. Raczyńska
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemical ◽  
Biologically Active ◽  
Deprotonation Reaction ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Scanty Information ◽  
Derivatives Of ◽  
Common Anion ◽  
Tautomeric Mixture

Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules.

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