scholarly journals Ab Initio Calculation of Nuclear Magnetic Resonance Chemical Shift Anisotropy Tensors 1. Influence of Basis Set on the Calculation of 31P Chemical Shifts

10.2172/833 ◽  
1998 ◽  
Author(s):  
T.M. Alam
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Ab Initio ◽  
Ab Initio Calculation ◽  
Chemical Shifts ◽  
Chemical Shift Anisotropy ◽  
Basis Set ◽  
Nuclear Magnetic

Carbon-13 Nuclear Magnetic Resonance Studies of Some Methyl Substituted Diphenylmethanes

1974 ◽  
Vol 52 (18) ◽  
pp. 3196-3200 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Giorgio Montaudo ◽  
Paolo Finocchiaro
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Ring Current ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic

Carbon-13 n.m.r. chemical shifts are reported for diphenylmethane and nine methylated derivatives. Results are compared with those for related methylbenzenes. In the case of tri-ortho-substituted materials the predominance of a perpendicular conformation is suggested. Ring current calculations show that in contrast to the 1H chemical shift interpretations, the 13C shielding trends cannot originate primarily from anisotropic effects.

Use of Replaced Chalcones to Generate a 13C Chemical Shift Staging Factor for Chalcone and Its Derivate

2020 ◽  
Vol 12 (4) ◽  
pp. 464-472
Author(s):  
Thaís F. Giacomello ◽  
Gunar V. da S. Mota ◽  
Antônio M. de J. C. Neto ◽  
Fabio L. P. Costa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Scaling Factor ◽  
Orbital Method ◽  
Beneficial Effects ◽  
Nuclear Magnetic

Chalcones have attracted the attention of researchers for decades, they are biologically classified as secondary metabolites of low molecular weight. These are considered as the precursors of flavonoids and they are widely distributed in plants such as vegetables, fruits, teas and spices. It has been demonstrating that chalcones possess many important bioactivities including properties of antioxidants and other evidence of its potential beneficial effects on health. Chalcone compounds and its derivatives have been showing a growing interest in the therapeutic properties. Nuclear magnetic resonance (NMR) spectroscopy is one of the most important tools for determining the structures of organic molecules. In the work present a 13C Nuclear magnetic resonance chemical shift protocol of chalcones and derivative based on the application of scaling factor with chalcone molecules. This protocol consists of using density functional theory with gauge-including atomic orbital method to calculating 13C chemical shifts and the application of a parameterized scaling factor in order to ensure accurate structural determination of chalcones and derivative.

Nonuniform backbone conformation of deoxyribonucleic acid indicated by phosphorus-31 nuclear magnetic resonance chemical shift anisotropy

Biochemistry ◽  
1980 ◽  
Vol 19 (3) ◽  
pp. 518-526 ◽  
Author(s):  
Heisaburo Shindo ◽  
Jan B. Wooten ◽  
Barbara H. Pheiffer ◽  
Steven B. Zimmerman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Deoxyribonucleic Acid ◽  
Chemical Shift Anisotropy ◽  
Backbone Conformation ◽  
Nuclear Magnetic

scholarly journals Structural and Theoretical Studies of 2-amino-3-nitropyridine

2012 ◽  
Vol 9 (4) ◽  
pp. 2191-2204 ◽  
Author(s):  
N. S. Al-Hokbany ◽  
A. A. Dahya ◽  
I. Kh. Warad ◽  
N. M. Abd El-Salam ◽  
S. T. Akriche ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Single Crystal ◽  
Chemical Shifts ◽  
Vibrational Analysis ◽  
Basis Set ◽  
Geometrical Parameters ◽  
X Ray ◽  
Bond Lengths ◽  
Nuclear Magnetic

Geometrical optimization, spectroscopic analysis, electronic structure and nuclear magnetic resonance of 2-amino-3-nitropyridine (ANP) were investigated by utilizingab-initio(MP2) and DFT(B3LYP) using 6-311++G(d,p) basis set. Geometrical parameters (bond lengths, bond angles and torsion angles) were computed and compared with the experimental values obtained using X-ray single crystal measurements of the title compound. IR spectra were obtained and assigned by vibrational analysis. Comparing the theoretically calculated values (bond lengths, bond and dihedral angles) using both B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) methods of calculations with the experimentally determined data by X-ray single crystal measurements, all the data obtained in this investigation were considered to be reliable. The theoretical infrared spectra have been successfully simulated by means of DFT and MP2 levels of calculations. The1H and13C nuclear magnetic resonance (NMR) chemical shifts of 2-amino-3-nitropyridine were calculated using the GIAO method in DMSO solution using IEF-PCM model and compared with the experimental data. Intramolecular hydrogen bonding interaction in this compound was investigated by means of the NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.

Nuclear Magnetic Resonance Study of Caesium-133 in Binary Molten Trifluoroacetate Salt Mixtures

2001 ◽  
Vol 56 (3-4) ◽  
pp. 288-290 ◽  
Author(s):  
V. N. Mirny ◽  
V. V. Trachevski ◽  
T. A. Mimaya
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Sodium Potassium ◽  
Salt Mixtures ◽  
Nuclear Magnetic

Abstract The chemical shifts of Cs+ in binary melts of caesium trifluoroacetate with lithium, sodium, potassium or thallium trifluoroacetates have been studied as a function of composition. An influence of added foreign cations on chemical shift of caesium nuclei has been found. The nature of the intra-and intermolecular paramagnetic contributions into the shifts of 133Cs is discussed.

Systematic Gauge-Including Atomic Orbital-Hybrid Density Functional Theory Linear Regressions for 13C NMR Chemical Shifts Calculation

2020 ◽  
Vol 12 (3) ◽  
pp. 364-370
Author(s):  
Sara Sâmitha Souza ◽  
Mariana Aparecida de Souza Martins ◽  
Antonio Maia de Jesus Chaves Neto ◽  
Gunar Vingre Da Silva Mota ◽  
Fabio Luiz Paranhos Costa
Keyword(s):  
Density Functional Theory ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Basis Set ◽  
Functional Theory ◽  
Linear Regressions ◽  
Nuclear Magnetic

Density-functional theory calculations of the magnetic shielding for nuclear magnetic resonance provide an important contribution to understand the experimental values obtained in laboratory for chemical shifts present in the samples. From of a comparative of the performance of ten hybrid functional within of the framework of the density-functional theory using 10 different hybrid functionals with 3-21G (B1), 6-31G(d) (B2) and 6-31+ G(d, p) (B3) basis set, with intuit of evaluating of performance of the 13 C nuclear magnetic resonance from a representative of the terpene class and a heterocyclic compound, (–)-loliolide ((7aR)-6-hydroxy-4,4,7a-trimethyl-6,7-dihydro-5H1-benzofuran-2-one). This molecule, satisfactorily, represents the main structure of this class, with conformational freedom, optical activity and a benzofuran nucleus. The ωB97X-D, MPW1K and HSEH1PBE functionals presented the best calculation performance. It is interesting to note that after the use of linear regressions all root mean square error values for ωB97X-D were lower than 3 ppm. These are 2.91 ppm (B1), 2.46 (B2) ppm and 2.62 ppm (B3). The information contained in this work can be used for the assignment of experimental nuclear magnetic resonance spectra and will motivate further studies involving the theoretical calculation of the chemical shift of 13C.

An Application of the Polarizable Continnum Model for Obtaining Chalcones Magnetic Properties

2020 ◽  
Vol 12 (7) ◽  
pp. 939-950
Author(s):  
Agnes Jalowitzki Silva ◽  
Thaís F. Giacomello ◽  
Gunar V. da S. Mota ◽  
Antônio M. de J. Chaves ◽  
Fabio L. P. Costa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Population Distribution ◽  
Chemical Shifts ◽  
Biological Activities ◽  
Geometry Optimization ◽  
Analytical Techniques ◽  
Spectroscopic Techniques ◽  
Nuclear Magnetic

Chalcones exhibit a wide variety of beneficial biological activities. In addition, these compounds include the prevention of diseases related to oxidative stress. The structural characterization of these molecules by means of analytical techniques can become a difficult task due to the complexity of some structures. However, cases of erroneously established natural product structure review are still found in the literature despite recent advances in spectroscopic techniques. Therefore, it is necessary to develop quantum calculation protocols that can aid in the correct structural ascertainment of these compounds. Thus, in this work, we tried to develop a parameterized protocol for calculations of chemical shift of carbon-13 nuclear magnetic resonance, in order to ensure a correct structural determination of polyphenols, with a focus on chalcones. For this, a series of molecules belonging to this class, with complex and varied structural skeletons, reliably elucidated in the literature, was selected and subjected to stochastic conformational searches using the Monte Carlo method and the Merk molecular force filed. The lower energy conformations of each molecule were selected for the geometry optimization step, performed at the mPW1PW91/6-31G(d) level. The chemical shifts of carbon-13 were calculated at the same level of theory, taking into account the population distribution of Boltzmann. The calculations were affected in both liquid phases, using the Polarizable Continuous Model as an implicit solvation model. The results show that the level of theory applied in the liquid phase allows a good reproduction of the experimental data. The application of the scaling factor allows the cancellation of systematic errors, which means that the values of scaled chemical shift are closer to the experimental ones. Thus, the parameterized protocol proved to be an important tool for the structural elucidation of polyphenols by calculations of carbon-13 nuclear magnetic resonance chemical shifts.

13C Nuclear Magnetic Resonance of Oximes. I. Solvent and Isotope Effects on the 13C Chemical Shifts of Acetoxime

1972 ◽  
Vol 50 (12) ◽  
pp. 1956-1958 ◽  
Author(s):  
N. Gurudata
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Solvent Effects ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Solvent Interactions ◽  
13C Chemical Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The 13C n.m.r. spectrum of acetoxime has been obtained in five representative solvents and the chemical shifts of the three carbon atoms measured. The solvent effects on the chemical shifts are found to reflect specific solute–solvent interactions. The effect of deuteration of the α-protons on the chemical shift of the oximino carbon is also discussed.

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