Nuclear magnetic resonance and molecular orbital study of phenylphosphine and some dihalogeno derivatives

1978 ◽  
Vol 74 ◽  
pp. 933 ◽  
Author(s):  
William J. E. Parr
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Nuclear Magnetic

Nuclear magnetic resonance and molecular orbital study of some cocaine analogues

Tetrahedron ◽  
1999 ◽  
Vol 55 (34) ◽  
pp. 10537-10546 ◽  
Author(s):  
Anu J. Airaksinen ◽  
Kari A. Tuppurainen ◽  
Simo E. Lötjönen ◽  
Matthias Niemitz ◽  
Meixiang Yu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Cocaine Analogues ◽  
Nuclear Magnetic

Self-Consistent Field–Molecular Orbital (SCF–MO) Calculations and Nuclear Magnetic Resonance Measurements for Fosfomycin and Related Compounds

1987 ◽  
Vol 76 (9) ◽  
pp. 753-756 ◽  
Author(s):  
Yves G. Smeyers ◽  
A. Hernández Laguna ◽  
F.J. Romero-Sánchez ◽  
M. Fernández-Ibañez ◽  
E. Galvez-Ruano ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Mo Calculations ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Related Compounds ◽  
Nuclear Magnetic

1H nuclear magnetic resonance and molecular orbital estimates of the internal rotational barrier in phenylpropynal in solution and in the vapor

1992 ◽  
Vol 70 (9) ◽  
pp. 2365-2369 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Robert W. Schurko
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Sets ◽  
Am1 Calculations ◽  
Internal Barrier ◽  
The One ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectra of phenylpropynal and 1-phenylpropyne are analyzed for CS2/C6D12 and acetone-d6 solutions. The ensuing spin–spin coupling constants over eight formal bonds are used in assessing the conformational dependence of the one in the propynal derivative, as compared to the one over six bonds in benzaldehyde. The eight-bond coupling constant in phenylpropynal implies, via a hindered rotor model, that the twofold barrier to internal rotation is 5.9 ± 1.6 kJ/mol in both solutions. This number is much smaller than that for the internal barrier in benzaldehyde, reflecting the reduced π electron conjugation in phenylpropynal. Molecular orbital computations, with geometry optimization, confirm the essentially purely twofold internal barrier in the free propynal. The theoretical magnitudes are given for AM1 calculations, as well as for abinitio computations with STO-3G, 3-21G, 6-31G, and 6-31G* bases. To within experimental error, the barrier magnitudes from the split-valence basis sets agree with those obtained in solution.

1H nuclear magnetic resonance and molecular orbital studies of the conformations of 3-fluoroanisole

1989 ◽  
Vol 67 (6) ◽  
pp. 1027-1031 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Substituent Effects ◽  
Spin Coupling ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Minimal Basis ◽  
Parent Molecule ◽  
Nuclear Magnetic

The proximate spin–spin coupling constant between the methyl protons and the ring protons, 5J(H,OCH3), is extracted from a full analysis of the 1H and 19F nuclear magnetic resonance spectra of 3-fluoroanisole in CS2 and acetone-d6 solutions. The values of 5J(H,OCH3) imply that the less polar cis conformer is slightly more stable at 300 K than the more polar trans conformer in both solvents, in agreement with geometry-optimized STO-3G MO computations for the free molecule. The latter also find a higher barrier to internal rotation of the methoxy group for 3-fluoroanisole than for the parent molecule. The present results are compared with other measurements of the conformer ratio for the vapor and for solutions. The STO-3G and 6-31G structures of the cis and trans conformers are compared. The C—F bond length is computed more reliably with the minimal basis set, as is the COC bond angle. The internal angles of the benzene moiety are, of course, found more accurately with the 6-31G basis. The computations indicate additivity of the substituent effects on the internal angle, as found experimentally for a variety of benzene derivatives. Keywords: 1H NMR of fluoroanisole, conformations of fluoroanisole, molecular orbital calculations for fluoroanisole.

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