Isolation of the Pyrrolizidine Alkaloid Intermedine-N-oxide from Cerinthe glabra and ab initio Calculation of its 13C NMR Shifts

2012 ◽  
Vol 67 (5) ◽  
pp. 411-416 ◽  
Author(s):  
Markus Luber ◽  
Arafa Musa ◽  
Hazem A. Kadry ◽  
Franz Bracher
Keyword(s):  
Ab Initio ◽  
13C Nmr ◽  
Ab Initio Calculation ◽  
Pyrrolizidine Alkaloid ◽  
Basis Sets ◽  
Good Accordance ◽  
Experimental Values ◽  
First Time ◽  
Nmr Signals ◽  
C Nmr

The pyrrolizidine alkaloid intermedine-N-oxide was isolated from Cerinthe glabra for the first time. Due to the questionable assignments of NMR signals of this compound in previous literature reports ab initio calculations of the 13C NMR values based on the GIAO approach, using HF and B3LYP levels of theory and the four basis sets 6-31G(d), 6-311G(d), 6-31G(d,p), and 6-311G(d,p) were performed. The assignments obtained this way are in very good accordance with the experimental values.

Preparation, 1H and 13C NMR, and ab initio/IGLO study of mono-O-protonated deltic acid and theoretical investigation of di-, tri-, and tetra-O-protonated deltic acids

1999 ◽  
Vol 77 (5-6) ◽  
pp. 525-529 ◽  
Author(s):  
GK Surya Prakash ◽  
Golam Rasul ◽  
George A Olah ◽  
Ronghua Liu ◽  
Thomas T Tidwell
Keyword(s):  
Nmr Spectroscopy ◽  
Ab Initio ◽  
Theoretical Investigation ◽  
13C Nmr ◽  
Chemical Shifts ◽  
1H And 13C Nmr ◽  
Nmr Chemical Shifts ◽  
Molar Solution ◽  
Protonated Species ◽  
C Nmr

The hitherto elusive mono-O-protonated deltic acid C3O3H3+ was prepared by protolysis of di-tert-butoxy deltate in FSO3H-SO2ClF and in FSO3H:SbF5 (Magic Acid; 1:1 molar solution) in SO2ClF as solvent at -78°C and was characterized by 1H and 13C NMR spectroscopy. The structure and NMR chemical shifts were also calculated by the ab initio/IGLO method. No NMR evidence was found for persistent di-O-protonated deltic acid under these conditions, although a limited equilibrium with the mono-O-protonated species can be involved. Di-, tri-, and tetra-O-protonated deltic acids were also studied by ab initio/IGLO method.Key words: protonated deltic acid, aromaticity, superacids, NMR spectroscopy, ab initio and IGLO calculations.

Gaussian basis sets for ab initio calculation of NLO properties of polyatomic molecules

2010 ◽  
Vol 10 (3-6) ◽  
pp. 239-256
Author(s):  
Diego Paschoal ◽  
Marcello F. Costa ◽  
Georgia M.A. Junqueira ◽  
Hélio F. Dos Santos
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Polyatomic Molecules ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Nlo Properties

Organoboranes and tetraorganoborates studied by 11B and 13C NMR spectroscopy and DFT calculations

2015 ◽  
Vol 70 (6) ◽  
pp. 421-424 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
13C Nmr ◽  
Quantum Chemical ◽  
13C Nmr Spectroscopy ◽  
Coupling Constants ◽  
Line Widths ◽  
Nmr Signals ◽  
C Nmr ◽  
Extract Information

AbstractCare should be taken on recording the sometimes elusive 13C NMR signals for boron-bonded carbon atoms, since it is easy to extract information about coupling constants 1J(13C,11B) by measuring the respective line widths of 13C(B-C) and 11B NMR signals. This information can be confirmed by quantum-chemical calculations [B3LYP (6-311+G(d,p) level of theory] of nJ(13C,11B) in organoboranes and tetraorganoborates. For the latter, the signs for n = 2, 3, 4 were experimentally determined.

The vibrational spectrum, barrier to internal rotation, and ab initio calculations of 2-chloropropane

1991 ◽  
Vol 69 (11) ◽  
pp. 1845-1856 ◽  
Author(s):  
J. F. Sullivan ◽  
Aiying Wang ◽  
Mei-Shiow Cheng ◽  
J. R. Durig
Keyword(s):  
Vibrational Spectrum ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Internal Rotation ◽  
Far Infrared ◽  
Basis Sets ◽  
Equilibrium Geometry ◽  
Coupling Term ◽  
Hartree Fock ◽  
Experimental Values

The Raman spectra (3200–50 cm−1) of gaseous, liquid, and solid 2-chloropropane-d3 (isopropyl-d3 chloride), CH3(CD3)CHCl, and the infrared spectra (3200–50 cm−1) of the gas and solid have been recorded. The torsional transitions observed in the far infrared spectrum of the gaseous sample recorded at a resolution of 0.10 cm−1 between 265 and 135 cm−1 were analyzed in terms of the semirigid rotor model. An effective barrier of 1378 ± 4 cm−1 (3.94 ± 0.01 kcal/mol), cosine–cosine coupling term of 166 ± 10 cm−1 (0.47 ± 0.03 kcal/mol), and sine–sine coupling term of −173 ± 1 cm−1 (−0.49 ± 0.01 kcal/mol) were determined by fitting ten observed frequencies arising from the CH3 and CD3 torsions. The assignment of the 27 fundamentals is given and discussed. A complete equilibrium geometry, barrier to internal rotation, and vibrational frequencies have been determined by ab initio Hartree–Fock gradient calculations employing either 3-21G* or 6-31G* basis sets for both the d0 and d3 species. These calculated results are compared to the experimental values as well as to the corresponding quantities for some similar molecules. Key words: 2-chloropropane, vibrational spectrum; ab initio calculations; barrier to internal rotation.

The simplified ab initio method calculation of linear polarizability

1973 ◽  
Vol 26 (5) ◽  
pp. 921 ◽  
Author(s):  
RD Brown ◽  
GR Williams
Keyword(s):  
Ab Initio ◽  
Small Molecules ◽  
Basis Set ◽  
Basis Sets ◽  
Orbital Method ◽  
Polarizability Anisotropy ◽  
Minimal Basis ◽  
Hartree Fock ◽  
Numerical Performance ◽  
Experimental Values

The simplified ab-initio molecular-orbital method described previously is particularly suited to the calculation of polarizabilities by the non-perturbative coupled Hartree-Fock technique. Trial calculations on CO and HF, for which comparison with corresponding ab-initio calculations is possible, show that the method gives an adequate numerical performance. Minimal basis set calculations in general tend to give values that are considerably too low because of inadequate flexibility of the basis and this is the origin of the large discrepancy between theory and experiment, especially for small molecules. ��� Results are also reported for N2O and O3. For these larger systems the SAI results with minimal basis sets are noticeably nearer experimental values. The polarizability anisotropy for N2O is particularly well reproduced by the SAI method. �

A THEORETICAL INVESTIGATION OF STRUCTURAL, SPECTROSCOPIC AND THERMODYNAMIC PROPERTIES OF CYCLODECANE

2007 ◽  
Vol 06 (02) ◽  
pp. 281-299 ◽  
Author(s):  
DALVA E. C. FERREIRA ◽  
WAGNER B. DE ALMEIDA ◽  
HÉLIO F. DOS SANTOS
Keyword(s):  
Quantum Chemical ◽  
Nmr Spectra ◽  
Energy Surface ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Torsion Potential ◽  
Good Accordance ◽  
First Time ◽  
Good Agreement ◽  
C Nmr

The torsion potential energy surface for cyclodecane has been examined using molecular mechanics and quantum chemical methods. The boat-chair-boat (BCB) conformer is predicted as the most stable structure at all levels of theory employed, in agreement with low temperature experiments. We found 13 low-energy conformers that cover a range of ~10 kcal mol-1. The relative abundance of the main isomers (named BCB, TBC, TBCC and TCCC) as a function of the temperature is discussed. In addition, energy calculations at high correlated levels of theory (MP4(SDTQ) and CCSD(T)) were for the first time performed for these conformations. In general, the predicted Gibbs population is in fairly good agreement with the experimental data. The simulated IR, VCD and 13 C NMR spectra were obtained showing good accordance with the observed data, providing important features for conformational analysis of cyclodecane.

scholarly journals Intermolecular Potential Function for Copper (II)-Water Based on ab initio Calculations

1990 ◽  
Vol 45 (2) ◽  
pp. 184-188
Author(s):  
Saiful Islam ◽  
E. H. S. Anwander ◽  
M. M. Probst ◽  
B. M. Rode
Keyword(s):  
Ab Initio ◽  
Potential Function ◽  
Ab Initio Calculation ◽  
Energy Surface ◽  
Pair Potential ◽  
Basis Sets ◽  
Intermolecular Potential ◽  
Double Zeta ◽  
Dynamics Simulations ◽  
Effective Core Potentials

AbstractAn analytical pair potential function for the system Cu(II)-water has been derived by means of ab initio calculation of the corresponding energy surface, using double zeta + polarization basis sets and effective core potentials. Tests on the function show that it should be reliable for use in Monte Carlo or molecular dynamics simulations.

Ab Initio Calculation of Molecular Properties of Cyanopolyynes, H—(C≡C)n—CN

1982 ◽  
Vol 37 (11) ◽  
pp. 1272-1275
Author(s):  
Tae-Kyu Ha ◽  
Minh Tho Nguyen
Keyword(s):  
Physical Properties ◽  
Ab Initio ◽  
Chain Length ◽  
Ab Initio Calculation ◽  
Molecular Properties ◽  
Rotational Constants ◽  
Experimental Values ◽  
Scf Calculations

Results of ab initio SCF calculations on cyanopolyynes, H-(C ≡ C)n-CN with n up to 7 are reported. Calculated rotational constants and one-electron properties are compared with the available experimental values. The effects of the C ≡ C chain length on the physical properties are discussed.

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