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.

Stereospecific synthesis, 1H and 13C NMR spectroscopy, and X-ray crystallographic studies of 6,6-dibromo-3α-cyano-2,2-dimethylpenam-(1R)-S-oxide

1991 ◽  
Vol 69 (3) ◽  
pp. 578-583 ◽  
Author(s):  
Claudio J. Salomon ◽  
Oreste A. Mascaretti ◽  
Charles E. Strouse ◽  
G. Punte
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Single Crystal ◽  
Crystal Packing ◽  
Stereospecific Synthesis ◽  
Nmr Studies ◽  
X Ray ◽  
Cell Parameters ◽  
Penicillin Sulfoxide ◽  
Nuclear Magnetic

A stereospecific synthesis of 6,6-dibromo-3α-cyano-2,2-dimethylpenam-(1R)-S-oxide (2) is described. The X-ray single crystal investigation of this compound shows that it crystallizes in the monoclinic system, space group P21, with cell parameters a = 6.194(1), b = 9.363(1), c = 9.869(1) Å, β = 96.55(2)°, V = 568(1) Å3, and two molecules per unit cell. Thestructure was solved, from low temperature data, by direct methods, and refined, by least-squares procedures, to a final R = 3.17%, Rw = 3.38%, for 1221 observed independent reflections. The sulfoxide configuration is R. The thiazolidine presents an envelope shape with the C(3) atom 0.56 Å above the other four members of the ring mean plane. Therefore, it exhibits the conformation with α-CH3 pseudoequatorial and β-CH3 and α-CN both pseudoaxial. This conformation is different from the one reported for other penicillin sulfoxide derivatives. The geometry of the β-lactam ring is typical of the fused bicyclic penam nucleus. The ring is non-planar. The N(4) atom displays a pyramidial arrangement. The examination of crystal packing shows that molecules along a are connected by a short C—H … O contactReported single crystal studies showed two dominant conformations for the thiazolidine ring in the fused bicyclic penam nucleus: the C(3) or 2β-3α substituents both pseudoaxial, as found in 2, and the S(1) or 2β-3α substituents both pseudoequatorial, adopted by most sulfoxides. Neither of these conformations can explain the nuclear Overhauser effect data. A conformation with the substituents C2-β-methyl-C3-α-H and C2-α-methyl-C3-α-CN fully eclipsed is in accordance with the experimental results in the solution. The 1H nuclear magnetic resonance data reflect the influence of the magnetic anisotropy of the CN triple bond on the gem-dimethyl groups, particularly in relation with the geometrical features of the molecule. Comparison of 13C nuclear magnetic resonance chemical shifts for 2 and its parent penicillin sulfide (1) indicates configurationally dependent substituent effects, the magnitude of which can be used for the stereochemical assignment of sulfoxide groups in this series. Key words: penicillin sulfoxide derivatives, di-halogen penicillanates, stereospecific synthesis, NMR studies, absolute configuration determination.

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.

Iodide ion receptors: shape-persistent macrocycles of syn/anti Configurations

2021 ◽  
Author(s):  
Guang-Wei Zhang ◽  
Jia-Yin XIANG ◽  
Tao-Tao Zhong ◽  
Xin-Ru ZHI ◽  
Chuang Gao ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Single Crystal ◽  
1H Nmr ◽  
X Ray ◽  
Macrocyclic Receptors ◽  
Iodide Ion ◽  
1H Nuclear Magnetic Resonance ◽  
Ion Receptors ◽  
Nuclear Magnetic

This article reports a pair of rigid iodide ion macrocyclic receptors of syn/anti configurations. Single crystal X-ray analysis confirms the structure of the syn-isomers, 1H Nuclear Magnetic Resonance (1H NMR)...

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