Indirekte Kernspinkopplung zwischen Protonen und Elementen der IV. Gruppe

1964 ◽  
Vol 19 (1) ◽  
pp. 139-142 ◽  
Author(s):  
Herbert Dreeskamp
Keyword(s):  
Electron Density ◽  
Strong Correlation ◽  
Valence Electron ◽  
Spin Coupling ◽  
Atomic Data ◽  
Coupling Constant ◽  
Methyl Group ◽  
Hartree Fock ◽  
Fermi Contact ◽  
Spin Spin Coupling

The indirect spin-spin coupling between protons and Ge73, spin 9/2, in the tetraedric molecule GeH4 has been measured. JGe-H = 97,6 Hz. Introducing the normalized coupling constant J′ which is obtained by dividing the measured coupling constant by the product of the magnetogyric ratios of the coupling nuclei, a strong correlation is found between this quantity for XH4 (X = C, Si, Ge, Sn, Pb) and the electron density of the valence electron at the nucleus obtained from HARTREE-FOCK calculations or experimental atomic data. This demonstrates that at least in these cases the FERMI contact contribution is dominant. For the analogeous tetramethyl compounds the same relation holds only to the extend that the C - H coupling in the methyl group is constant.

Berechnung der Spin-Spin-Koppelkonstante von HD mit nichtsingulärem Kontaktoperator / Calculation of the NMR Coupling Constant in HD by Using a Nonsingitlar Contact Operator

1973 ◽  
Vol 28 (11) ◽  
pp. 1866-1868 ◽  
Author(s):  
W. Sänger ◽  
J. Voitländer
Keyword(s):  
Delta Function ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Coupling Energy ◽  
First Order ◽  
Order Energy ◽  
Spatial Part ◽  
Fermi Contact ◽  
Contact Operator ◽  
Spin Spin Coupling

The Fermi contact contribution to the nuclear spin-spin coupling constant of HD is calculated variationally. Instead of the delta-function a modified nonsingular contact spatial part is used. The self-coupling energy becomes finite and the variation of the whole second-order energy due to a non- singular first-order perturbed trial function can be carried out.

Anisotropy of indirect spin–spin coupling constants from nuclear magnetic resonance powder patterns of rigid solids. 1J(31P,199Hg) in [HgP(o-tolyl)3(NO3)2]2

1988 ◽  
Vol 66 (8) ◽  
pp. 1821-1823 ◽  
Author(s):  
Glenn H. Penner ◽  
William P. Power ◽  
Roderick E. Wasylishen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constants ◽  
Fermi Contact ◽  
Spin Spin Coupling ◽  
Contact Mechanism ◽  
Nuclear Magnetic

The anisotropy of the indirect 31P,199Hg spin–spin coupling constant, ΔJ, in solid [HgP(o-tolyl)3(NO3)2]2 is obtained from an analysis of the 31P nuclear magnetic resonance powder pattern. The value of ΔJ, 5170 ± 250 Hz, is large and indicates that mechanisms other than the Fermi contact mechanism are important for this spin–spin coupling. The powder spectrum also indicates that the absolute sign of 1J(31P,199Hg) is positive.

INDO MO Calculations of the Conformational Dependence of the vicinal 13C,H Spin–Spin Coupling Constant in Propane

1972 ◽  
Vol 50 (16) ◽  
pp. 2710-2712 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Coupling Constant ◽  
Mo Calculations ◽  
Orbital Theory ◽  
Angle Dependence ◽  
Proton Coupling ◽  
Fermi Contact ◽  
Spin Spin Coupling

Molecular orbital theory at the INDO level of approximation is used to calculate the Fermi contact contribution to three-bond carbon–proton coupling constants in propane. The calculations predict a dihedral angle dependence of 3J(13C,H) in the 13C—C—C—H fragment similar to that observed for 3J(H,H), 3J(19F,H), and for 3J(31P,H) in the saturated X—C—C—H fragments.

The probable planarity of 1,2-dimethoxybenzene in solution

1983 ◽  
Vol 61 (2) ◽  
pp. 224-229 ◽  
Author(s):  
Ted Schaefer ◽  
Reino Laatikainen
Keyword(s):  
Benzene Solution ◽  
Theoretical Data ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Methyl Group ◽  
H Nmr ◽  
Planar Conformation ◽  
Precise Analysis ◽  
Spin Spin Coupling

A precise analysis of the 1H nmr spectrum of 1,2-dimethoxybenzene in benzene solution yields an accurate value for the proximate spin–spin coupling constant, [Formula: see text], between the ortho ring proton and the methyl protons. The latter also couple to other ring protons and these couplings are assessed. Comparison with some values in other anisole derivatives and with a variety of INDO MO FPT calculations of [Formula: see text] strongly implies the predominance of a planar conformation in solution. This implication disagrees with the interpretation of some other experimental and theoretical data. The mechanism of this proximate coupling is examined by the procedure of Barfield. It seems that the magnitude of the coupling is dominated by interactions involving the orbitals on the carbon atom of the methyl group.

The range of in anisole derivatives. An indicator of torsion and compression of the methoxy group

1985 ◽  
Vol 63 (3) ◽  
pp. 782-786 ◽  
Author(s):  
Ted Schaefer ◽  
Salman R. Salman ◽  
Timothy A. Wildman ◽  
Glenn H. Penner
Keyword(s):  
Methoxy Group ◽  
Bond Angle ◽  
Average Distance ◽  
Electron Donors ◽  
Spin Coupling ◽  
Ortho Position ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Methyl Group ◽  
Spin Spin Coupling

In a series of anisole derivatives, [Formula: see text], the spin–spin coupling constant between the methyl protons and the ring proton in the ortho position, ranges from −0.23 to −0.38 Hz when the methyl group lies cis to the ortho C—H bond. 5J, as a proximate coupling, is sensitive to the average distance between the coupled protons. Its variation with substituent can be rationalized in terms of torsion about the Csp2—O bond and changes in the bond angles near the methoxy moiety. The theoretical 5J numbers can be empirically reproduced by a cos4 ψ function, where ψ is the angle by which the methoxy group twists out of the benzene plane. In general, large ortho substituents cause an increase in the magnitude of 5J (bond angle changes), strong π electron donors in the para position cause a decrease in the magnitude of 5J (increased torsional freedom), and π electron acceptors do the opposite (decreased torsions).

The sign of the 'through-space' spin–spin coupling between methyl protons and the fluorine nucleus in 2,6-dimethylbenzoyl fluoride

1976 ◽  
Vol 54 (5) ◽  
pp. 800-804 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum ◽  
Kirk Marat ◽  
Roderick E. Wasylishen
Keyword(s):  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Fluorine Nucleus ◽  
Methyl Group ◽  
Out Of Plane ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms ◽  
Carbonyl Fluoride

The spin–spin coupling constant over five formal bonds between 19F and methyl protons, [Formula: see text], in 2,6-dimethylbenzoyl fluoride is −3.1 Hz. Observation of a nonzero [Formula: see text] indicates an out-of-plane conformation for the carbonyl fluoride group and implies substantial nonbonded repulsions between the methyl and carbonyl fluoride groups. It is argued that [Formula: see text] is as small as −7 Hz when the C—F bond lies cis to a methyl group and that its magnitude is a consequence of the so-called 'through-space' coupling mechanisms. On the basis of INDO–MO–FPT computations, it is suggested that such observed couplings are a composite of large contributions of either sign and, therefore, that observed through-space 1H,19F couplings may be of either sign if conformational averaging occurs.

Carbon-Nitrogen Spin-Spin Coupling in Diazomethane

1976 ◽  
Vol 31 (11) ◽  
pp. 1515-1518 ◽  
Author(s):  
W. Runge ◽  
J. Firl
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Fermi Contact ◽  
Nitrogen Coupling ◽  
The One ◽  
Spin Spin Coupling ◽  
Contact Mechanism

The one-bond carbon-nitrogen coupling constant of diazomethane is reported. Analogies with carbon-carbon coupling constants in allenes are emphasized. CNDO/S-calculations are used as a support of the suggestions the C-N coupling in diazomethane to be dominated by the Fermi contact mechanism and the sign of the carbon-nitrogen-15 coupling constant to be negative

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