Long-Range 31P-31P Spin Coupling Constants in the 31P NMR Spectra of Phosphite Triesters

1996 ◽  
Vol 111 (1) ◽  
pp. 71-71
Author(s):  
Andrew Riley ◽  
Stephen Mills ◽  
Barry Potter
Keyword(s):  
Long Range ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Coupling Constants ◽  
Spin Coupling ◽  
31P Nmr Spectra ◽  
Spin Coupling Constants

scholarly journals Signs of proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine. Sigma and pi contributions to coupling in a nitrogen heterocycle

1969 ◽  
Vol 47 (9) ◽  
pp. 1507-1514 ◽  
Author(s):  
T. Schaefer ◽  
S. S. Danyluk ◽  
C. L. Bell
Keyword(s):  
Nitrogen Atom ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nitrogen Heterocycle ◽  
Triple Resonance ◽  
Triple Resonance Experiments ◽  
Proton Proton ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The signs of all proton–proton and proton–fluorine spin–spin coupling constants in 2-fluoro-3-methylpyridine have been determined by double and triple resonance experiments. The signs of the longrange coupling constants, JH,CH3 and JF,CH3 are the same as in fluorotoluene derivatives. Their magnitudes are consistent with the assumption that the nitrogen atom primarily polarizes the σ bonds in the molecule, leaving the π contribution to the long-range coupling relatively unaffected.

A proton magnetie resonance and molecular orbital study of the conformational preferences of the vinylic fragment in some 2-vinylfurans and in 2-vinylthiophene

1976 ◽  
Vol 54 (20) ◽  
pp. 3216-3223 ◽  
Author(s):  
William J. E. Parr ◽  
Roderick E. Wasylishen ◽  
Ted Schaefer
Keyword(s):  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Orbital Theory ◽  
Molecular Orbital Study ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The stereospecific spin–spin coupling constants over five bonds between the α-proton in the side chain and the protons in the heterocycle in 2-vinylfuran, in its β-nitro and β-aldehydic derivatives, and in 2-vinylthiophene are used to demonstrate the preponderance of the s-trans conformers in polar and nonpolar solutions. These conclusions are compared with predictions made by molecular orbital theory at the STO-3G, INDO, CNDO/2, and MINDO/3 levels. Long-range coupling constants between the protons in the side chain and protons in the heterocycle are calculated by CNDO/2 and INDO–MO–FPT and are compared with experiment. It is concluded that the five-bond couplings involving the α-proton are most sensitive to conformation and that they are transmitted mainly via a σ electron mechanism. The other long-range coupling constants are discussed in terms of σ and π electron mechanisms. The STO-3G calculations yield barriers to internal rotation of greater than 4.8 kcal/mol.

NMR spectra, MO calculations of spin-spin coupling constants and conformational analysis of substituted 1,3-dioxolanes

1980 ◽  
Vol 13 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Rois Benassi ◽  
Luisa Schenetti ◽  
Ferdinando Taddei ◽  
Luigi Villa ◽  
Vincenzo Ferri
Keyword(s):  
Conformational Analysis ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Mo Calculations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling
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