ChemInform Abstract: LONG-RANGE COUPLING IN THE NUCLEAR MAGNETIC RESONANCE SPECTRA OF PYRROLE DERIVATIVES (I)

1974 ◽  
Vol 5 (7) ◽  
Author(s):  
EMANUELE DRADI ◽  
GIAMPAOLO TOSOLINI ◽  
VITTORIO VECCHIETTI
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Pyrrole Derivatives ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Fluorine magnetic resonance studies. III. Fluorine-fluorine coupling over six and seven bonds in fluorostyrenes

1977 ◽  
Vol 30 (3) ◽  
pp. 543 ◽  
Author(s):  
DA Burgess ◽  
ID Rae ◽  
JD Snell
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Aromatic Ring ◽  
Long Range ◽  
Magnetic Resonance Studies ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 19F nuclear magnetic resonance spectra of β,β-difluorostyrenes and 1-difluoromethyleneindans bearing fluorine substituents in the aromatic ring have been recorded and the long-range couplings 6JF,F and 7JF,F are discussed. In each compound the larger couplings are to the olefinic fluorine trans to the aromatic ring. The couplings are maximum in the planar indans, reducing to unobservable values when non-planarity is achieved in suitably substituted styrenes. The allylic coupling 4JH,F involving olefinic fluorines shows only slight stereochemical dependence.

Molecular orbital calculations and 1H nuclear magnetic resonance spectra as indicators of internal rotational potentials in some methyl derivatives of styrene

1988 ◽  
Vol 66 (4) ◽  
pp. 584-590 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectra of the α-methyl, cis and trans-β-methyl, 4-methyl, and β,β-dimethyl styrènes are analyzed to yield long-range proton–proton coupling constants. With the assumptin that the internal rotational potential for styrene in the gas phase is unaltered in solution, a consistent treatment of over 40 of the long-range coupling constants is given in terms of the known coupling mechanisms. Expectation values of sin2 θ, where θ is the angle of twist about the exocyclic carbon–carbon bond, are presented for these molecules. These are compared with theoretical potentials at the 6-31 G level of molecular orbital theory. The present data indicate rather larger average twist angles than those in the literature. The extrema (at θ = θ° and 90°) in the angle dependent long-range coupling constants appear to be rather smaller in magnitude than are theoretical values obtained from valence bond and molecular orbital approaches.

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