Through-space or proximate 19F,19F and 19F,1H spin–spin coupling constants in some benzenesulfonyl fluoride derivatives

1976 ◽  
Vol 54 (22) ◽  
pp. 3564-3568 ◽  
Author(s):  
William J. E. Parr ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Conformational Preference ◽  
Fluorine Nucleus ◽  
Spin Coupling Constants ◽  
The Difference ◽  
Spin Spin Coupling

The analysis of the fluorine and proton magnetic resonance spectra of 2,4,6-trimethylbenzenesulfonyl fluoride and of 2,5-difluorobenzenesulfonyl fluoride yields the signs and magnitudes of the spin–spin coupling constants containing a through-space component. The coupling between the fluorine nucleus and the methyl protons over five bonds is +1.9 Hz, opposite in sign to the −3.1 Hz observed for the corresponding coupling in 2,6-dimethylbenzoyl fluoride. The difference of 5 Hz is possibly a consequence of the different conformational preference of the SO2F and COF substituents. The coupling over four bonds between the fluorine nucleus on the side chain and that on the ring is +11.6 Hz in 2,5-difluorobenzenesulfonyl fluoride. It is argued that this value indicates a preference of the S—F bond for a plane lying, on average, nearly perpendicular to the benzene ring. Similar indications are noted for pentafluorobenzenesulfonyl fluoride and for pentafluorobenzenesulfinyl fluoride.

Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluenes VIII. Stereospecific 1H–9F Coupling Constants and Conformations of some Fluoro and Chloro Derivatives of Benzalchloride

1971 ◽  
Vol 49 (12) ◽  
pp. 2033-2036 ◽  
Author(s):  
H. M. Hutton ◽  
J. B. Rowbotham ◽  
B. H. Barber ◽  
T. Schaefer
Keyword(s):  
Proton Magnetic Resonance ◽  
Rotational Isomerism ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Fluorine Nucleus ◽  
Spin Coupling Constants ◽  
Chloro Derivatives ◽  
Spin Spin Coupling ◽  
Derivatives Of

In solution the 2-fluoro-5-chloro-, 2-fluoro-6-chloro-3-nitro-, 2-fluoro-6-chloro-5-nitro-, and 2,4,5-trichloro-benzalchlorides prefer conformations in which the C— bond of the side-chain lies in the plane of the aromatic ring. This C—H bond eclipses that ortho C—X bond (X = H, F, Cl) in which X is smaller than Y = H, F, Cl in the C—Y bond, also ortho to the dichloromethyl group. The long-range spin–spin coupling constants between the proton in the side-chain and the ring protons or fluorine nucleus are stereospecific. In particular, the coupling over four bonds between the side-chain proton and the ring fluorine is −0.3 Hz when the C—H and C—F bonds are arranged cis to each other but is −2.5 Hz when these bonds have a transoid planar arrangement.

A proton magnetic resonance determination of the small rotational barriers about the C—Si bond in phenyl derivatives of chloro and methyl silanes

1977 ◽  
Vol 55 (3) ◽  
pp. 557-561 ◽  
Author(s):  
William J. E. Parr ◽  
Ted Schaefer
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of ◽  
Low Energy Conformations

The long-range spin–spin coupling constants between protons bonded to silicon and ring protons in C6H5SiH3, C6H5SiH2Cl, C6H5SiH2CH3, C6H5SiHCl2, and C6H5SiH(CH3)2 are determined from the proton magnetic resonance spectra of benzene solutions. A hindered rotor treatment of the barrier to internal rotation about the C—Si bond, in conjunction with the coupling constants over six bonds, allows the deduction of the low-energy conformations for C6H5SiH(CH3)2 and for C6H5SiHCl2, as well as of barriers of 1.0 ± 0.2 kcal/mol. The approach becomes less reliable for C6H5SiH2CH3 and for C6H5SiH2Cl and, particularly for the latter compound, the derived barrier is very likely an upper limit only. Ab initio molecular orbital calculations of the conformational energies are reported for C6H5SiH3, C6H5SiH2Cl, and for C6H5SiHCl2.

Conformational dependence of long-range spin-spin coupling constants in 2,6-dichlorobenzylfluoride

1969 ◽  
Vol 47 (19) ◽  
pp. 3688-3690 ◽  
Author(s):  
T. Schaefer ◽  
C. M. Wong ◽  
K. C. Tam
Keyword(s):  
Magnetic Resonance ◽  
Long Range ◽  
Proton Magnetic Resonance ◽  
Resonance Spectrum ◽  
Double Resonance ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Double resonance experiments on the proton magnetic resonance spectrum of 2,6-dichlorobenzylfluoride yield the signs of the long-range coupling constants between the ring protons and the fluorine nuclei and protons in the fluoromethyl group. The signs and magnitudes of the long-range couplings are discussed in terms of their dependence on the conformation of the fluoromethyl group.

An estimate of the spin–spin coupling constant, 1J(1H,13C), in gaseous benzene

1996 ◽  
Vol 74 (8) ◽  
pp. 1524-1525 ◽  
Author(s):  
Ted Schaefer ◽  
Guy M. Bernard ◽  
Frank E. Hruska
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dielectric Constant ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Gaseous Benzene

An excellent linear correlation (r = 0.9999) exists between the spin–spin coupling constants 1J(1H,13C), in benzene dissolved in four solvents (R. Laatikainen et al. J. Am. Chem. Soc. 117, 11006 (1995)) and Ando's solvation dielectric function, ε/(ε – 1). The solvents are cyclohexane, carbon disulfide, pyridine, and acetone. 1J(1H,13C)for gaseous benzene is predicted to be 156.99(2) Hz at 300 K. Key words: spin–spin coupling constants, 1J(1H,13C) for benzene in the vapor phase; spin–spin coupling constants, solvent dielectric constant dependence of 1J(1H,13C) in benzene; benzene, estimate of 1J(1H,13C) in the vapor; nuclear magnetic resonance, estimate of 1J(1H,13C) in gaseous benzene.

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.

Experimental and Theoretical-Study of Carbon-Fluorine Couplings in the NMR-Spectra of 2-Fluoroaryl Ketones

1985 ◽  
Vol 38 (12) ◽  
pp. 1779 ◽  
Author(s):  
RH Contreras ◽  
CG Giribet ◽  
MA Natiello ◽  
J Perez ◽  
ID Rae ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Side Chain ◽  
Aliphatic Carbon ◽  
Spin Coupling Constants ◽  
Fermi Contact ◽  
Spin Spin Coupling ◽  
Fermi Contact Term ◽  
Good Agreement

Calculations by the IPPP-INDO method give the spin-spin coupling constants for the side-chain carbons, 3JCF and 4JCF, as 4.97 and 6.86 Hz respectively with substantial contributions to through-space coupling from the pathway CO-C-H…F. The observed values for 1-(2- fluorophenyl ) ethanone , 3.3 and 7.2 Hz, and for 1-(2,5- difluorophenyl ) ethanone , 3.7 and 7.3 Hz, are in good agreement with these predictions. Two compounds, a dihydroindenone and a naphthalenone, in which this pathway cannot be effective, show no fluorine coupling to the aliphatic carbon next to the carbonyl and the values of 3JCF are reduced to 2.2 and 2.5 Hz, consistent with the loss of a through-space Fermi contact term of the kind described above.

Preparation and Nuclear Magnetic Resonance Study of Phosphorus Compounds Containing Alkenyl Functional Groups

1974 ◽  
Vol 52 (9) ◽  
pp. 1714-1720 ◽  
Author(s):  
Peter W. Clark ◽  
John L. S. Curtis ◽  
Philip E. Garrou ◽  
George E. Hartwell
Keyword(s):  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Phosphorus Compounds ◽  
Proton Spectrum ◽  
Phosphine Oxides ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Proton Decoupling

The phosphines PPhn(CH2CH2CH=CH2)3−n, n = 2–0, PPhn(CH2CH2CH2CH=CH2)3−n, n = 1 or 2, and PPh2CH2CH = CH2 have been synthesized and studied by 1H and 31P magnetic resonance. The n.m.r. spectra of PPh2(OCH2CH=CH2), its oxide, O=PPh2(OCH2CH=CH2), and its Arbuzov rearrangement product, O=PPh2(CH2CH=CH2), have been investigated by 31P decoupling of the proton spectrum, selective proton decoupling of the 31P spectrum, and comparison with computer-simulated spectra to determine the spin–spin coupling constants. The n.m.r. spectra of the related oxides O=PPh2CH2CH2CH=CH2, O=P(CH2CH2CH=CH2)3, and O=P(OCH2CH=CH2)3 are also assigned. The data indicate that 3JPH > 2JPH for alkenylphosphines, 2JPH is larger for phosphine oxides than for phosphines, and 3JPH is little changed in comparing phosphorus(III) with phosphorus(V) compounds.

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