scholarly journals Three New Biflavonoids from Chinese Dragon's Blood, Dracaena cochinchinensis

2012 ◽  
Vol 7 (5) ◽  
pp. 1934578X1200700 ◽  
Author(s):  
Jing Guan ◽  
Shun-Xing Guo
Keyword(s):  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Chemical Calculation ◽  
Dragon’S Blood ◽  
Esi Ms ◽  
H Nmr ◽  
Cd Spectrum ◽  
The Absolute ◽  
Circular Dichroïsm ◽  
C Nmr

Three new biflavonoids, named (2 Rγ S)-3′-methoxy-8-methylsocotrin-4′-ol (1), (2 Sγ R)-3′-methoxy-8-methylsocotrin-4′-ol (2), and (2 Rγ R)-8-methylsocotrin-4′-ol (3), were isolated from Chinese Dragon's blood [Dracaena cochinchinensis (Lour.) S. C. Chen], together with two known ones. The structures of these new biflavonoids were elucidated by a combination of HR-ESI-MS, 1H NMR, 13C NMR, HMQC, and HMBC spectra. The absolute configurations of compounds 1-4 were determined by quantum chemical calculation of the circular dichroism spectrum and comparison with the experimental CD spectrum.

1H NMR study of cation solvation in the mixed solvent dimethylformamide-water

1985 ◽  
Vol 50 (11) ◽  
pp. 2325-2330 ◽  
Author(s):  
Petr Kyselka ◽  
Ivo Sláma
Keyword(s):  
Charge Transfer ◽  
Chemical Shift ◽  
1H Nmr ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Mixed Solvent ◽  
Chemical Calculation ◽  
H Nmr ◽  
Nmr Method ◽  
Nmr Study

Solvation effects of Li+, Na+, and Mg2+ on the mixed solvent dimethylformamide-water were investigated by the 1H NMR method. The dependence of the chemical shift of solvent protons on the mixed solvent composition was established for various concentrations of perchlorates. Isosolvation points were determined, and the dependences of charge transfer from solvent to cation on the chemical shift of solvent, as obtained by a quantum chemical calculation, were compared for the systems DMF-Mn+ and DMF-Mn+-H2O.

Quantum Chemical Calculation on 1H NMR Chemical Shifts of PMMA/PVPh Blends

2011 ◽  
Vol 301-303 ◽  
pp. 263-268 ◽  
Author(s):  
Wei Gui Fu ◽  
Li Chen ◽  
Bao Hui Li ◽  
Ping Chuan Sun
Keyword(s):  
Hydrogen Bonds ◽  
Polymer Blends ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Chemical Calculation ◽  
Oh Groups ◽  
H Nmr ◽  
Chain Conformations

Prediction of chemical shifts using quantum chemical calculation is helpful for assigning nuclear magnetic resonance (NMR) spectra, and very important in structure determination. In this paper, we calculated1H chemical shifts (δH) of poly (methyl methacrylate) (PMMA), poly (4-vinyl phenol) (PVPh) and their polymer blends. Density functional theory (DFT) was used to computeδH of hydroxyl groups (OH) for both PVPh homopolymer and PMMA/PVPh polymer blends. The calculated values forδH of OH groups with or without forming hydrogen bonds agreed reasonably well with the experimental values. It was found that the δH of OH groups moved downfield when they formed hydrogen bonds with both other OH groups and carbonyl groups (C=O). The simulated solid state1H NMR spectra based on the B3LYP // GIAO method yielded results for the PMMA, PVPh and PMMA/PVPh, showed excellent agreement with the experimental results. It indicates that the1H NMR spectra are influenced by the main-chain conformations and the hydrogen bond types.

Examination on Permittivity Estimation of Hydrocarbon-based Thermosetting Resin based on Quantum Chemical Calculation

2017 ◽  
Vol 137 (11) ◽  
pp. 626-631 ◽  
Author(s):  
Yuki Fuchi ◽  
Ryota Nakasako ◽  
Masahiro Kozako ◽  
Masayuki Hikita ◽  
Nobuhito Kamei
Keyword(s):  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Chemical Calculation ◽  
Thermosetting Resin

Effect of temperature on chiroptical and conformational properties of acyclic ketoses

1980 ◽  
Vol 45 (2) ◽  
pp. 475-481
Author(s):  
Slavomír Bystrický ◽  
Tibor Sticzay ◽  
Igor Tvaroška
Keyword(s):  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Conformational Mobility ◽  
Effect Of Temperature ◽  
Chemical Calculation ◽  
Cd Spectra ◽  
Conformational Properties ◽  
Temperature Dependences

Conformational mobility of tetruloses, 2-pentuloses, D-3-pentulose and 4-deoxy-L-pentulose was studied by measuring temperature dependences of CD spectra in the region +40°C to -140°C in a methanol-ethanol (1:4) mixture. The changes in spectra reflect the population of rotamers around bonds to the carbonyl chromophore. The most stable conformers were determined by PCILO quantum chemical calculation.

scholarly journals Preamble from the Guest Editor of Special Issue “DFT Quantum-Chemical Calculation of Metal Clusters”

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 442
Author(s):  
Oleg V. Mikhailov
Keyword(s):  
Guest Editor ◽  
Quantum Chemical Calculation ◽  
Quantum Chemical ◽  
Chemical Structure ◽  
Metal Clusters ◽  
Chemical Calculation ◽  
Special Issue

As known, the concept of “cluster” is collective and includes substances that are quite diverse in composition and chemical structure [...]

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