A Computational Study of the Isomerization of Prolyl Amides As Catalyzed by Intramolecular Hydrogen Bonding

2002 ◽  
Vol 106 (46) ◽  
pp. 11168-11172 ◽  
Author(s):  
Kathryn N. Rankin ◽  
Russell J. Boyd
Keyword(s):  
Hydrogen Bonding ◽  
Computational Study ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

scholarly journals A simple and effective preparation of quercetin pentamethyl ether from quercetin

2018 ◽  
Vol 14 ◽  
pp. 3112-3121 ◽  
Author(s):  
Jin Tatsuzaki ◽  
Tomohiko Ohwada ◽  
Yuko Otani ◽  
Reiko Inagi ◽  
Tsutomu Ishikawa
Keyword(s):  
Hydrogen Bonding ◽  
Dimethyl Sulfoxide ◽  
Room Temperature ◽  
Computational Study ◽  
Dimethyl Sulfate ◽  
Intramolecular Hydrogen Bonding ◽  
Single Product ◽  
Oh Groups ◽  
Methylation Product ◽  
Intramolecular Hydrogen

Among the five hydroxy (OH) groups of quercetin (3,5,7,3',4'-pentahydroxyflavone), the OH group at 5 position is the most resistant to methylation due to its strong intramolecular hydrogen bonding with the carbonyl group at 4 position. Thus, it is generally difficult to synthesize the pentamethyl ether efficiently by conventional methylation. Here, we describe a simple and effective per-O-methylation of quercetin with dimethyl sulfate in potassium (or sodium) hydroxide/dimethyl sulfoxide at room temperature for about 2 hours, affording quercetin pentamethyl ether (QPE) quantitatively as a single product. When methyl iodide was used in place of dimethyl sulfate, the C-methylation product 6-methylquercetin pentamethyl ether was also formed. A computational study provided a rationale for the experimental results.

Characterization of Hydrogen Bonds in the End-Functionalized Single-Wall Carbon Nanotubes: A DFT Study

NANO ◽  
2015 ◽  
Vol 10 (03) ◽  
pp. 1550036
Author(s):  
Reza Ghafouri ◽  
Fatemeh Ektefa ◽  
Mansour Zahedi
Keyword(s):  
Carbon Nanotubes ◽  
Hydrogen Bonding ◽  
Computational Study ◽  
Intramolecular Hydrogen Bonding ◽  
Nbo Analysis ◽  
Coupling Constants ◽  
Single Wall Carbon Nanotubes ◽  
Single Wall Carbon ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bondings

A systematic computational study is carried out to shed some light on the structure of semiconducting armchair single-wall carbon nanotubes (n, n) SWCNTs, n = 4, 5 and 6, functionalized at the end with carboxyl (– COOH ) and amide (– CONH 2) from the viewpoint of characterizing the intramolecular hydrogen bondings at the B3LYP/6-31++G(d, p) level. Geometry parameters display different types of intramolecular hydrogen bonding possibilities in the considered functionalized SWCNTs. All of the hydrogen bondings are confirmed by natural bonding orbitals (NBO) analysis as well as nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) parameters. Based on NBO analysis, the calculated [Formula: see text] delocalization energies E(2), 1.15 kcal/mol to 7.04 kcal/mol, are in direct relation with the hydrogen bonding strengths. Differences in the chemical shielding principal components of 13 C and 17 O nuclei correlate well with the strengths of the hydrogen bondings. Participating in stronger hydrogen bondings, a larger SWCNT has a decreasing effect on 13 C (= O ) and 17 O isotropic chemical shieldings, σiso, consistent with the NBO analysis. The considerable changes of 13 C /17 O σiso can be interpreted as a result of shielding tensor component orientation. The 13 C (= O ) and 17 O quadrupole coupling constants C Q decrease under the effect of hydrogen bonding while asymmetry parameters ηQ significantly increase, indicating that 17 O ηQ is more sensitive to hydrogen bondings.

scholarly journals A Family of Ethyl N-Salicylideneglycinate Dyes Stabilized by Intramolecular Hydrogen Bonding: Photophysical Properties and Computational Study

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3112
Author(s):  
Larisa E. Alkhimova ◽  
Maria G. Babashkina ◽  
Damir A. Safin
Keyword(s):  
Optical Properties ◽  
Hydrogen Bonding ◽  
Dft Calculations ◽  
Computational Study ◽  
Photophysical Properties ◽  
Luminescent Properties ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Proton Transfer ◽  
Polar Solvents ◽  
Intramolecular Hydrogen

In this work we report solvatochromic and luminescent properties of ethyl N-salicylideneglycinate (1), ethyl N-(5-methoxysalicylidene)glycinate (2), ethyl N-(5-bromosalicylidene)glycinate (3), and ethyl N-(5-nitrosalicylidene)glycinate (4) dyes. 1–4 correspond to a class of N-salicylidene aniline derivatives, whose photophysical properties are dictated by the intramolecular proton transfer between the OH-function and the imine N-atom, affording tautomerization between the enol-imine and keto-enamine forms. Photophysical properties of 1–4 were studied in different pure non-polar and (a)protic polar solvents as well as upon gradual addition of NEt3, NaOH, and CH3SO3H. The DFT calculations were performed to verify the structures of 1–4 as well as their electronic and optical properties.

Theoretical study of intramolecular hydrogen bonding and molecular geometry of 2-trifluoromethylphenol

10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai
Keyword(s):  
Hydrogen Bonding ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen
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