Approximate self-consistent molecular orbital theory of nuclear spin coupling. IV. Vicinal proton-proton coupling constants in substituted ethanes and ethylenes and related compounds

1970 ◽  
Vol 92 (15) ◽  
pp. 4497-4506 ◽  
Author(s):  
Gary E. Maciel ◽  
J. W. McIver ◽  
N. S. Ostlund ◽  
J. A. Pople
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Proton Proton ◽  
Proton Coupling ◽  
Self Consistent ◽  
Vicinal Proton ◽  
Related Compounds

Approximate self-consistent molecular orbital theory of nuclear spin coupling. III. Geminal proton-proton coupling constants

1970 ◽  
Vol 92 (14) ◽  
pp. 4151-4157 ◽  
Author(s):  
Gary E. Maciel ◽  
J. W. McIver ◽  
N. S. Ostlund ◽  
J. A. Pople
Keyword(s):  
Molecular Orbital ◽  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Self Consistent

Approximate self-consistent molecular orbital theory of nuclear spin coupling. I. Directly bonded carbon-hydrogen coupling constants

1970 ◽  
Vol 92 (1) ◽  
pp. 1-11 ◽  
Author(s):  
G. E. Maciel ◽  
J. W. McIver ◽  
N. S. Ostlund ◽  
J. A. Pople
Keyword(s):  
Molecular Orbital ◽  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Self Consistent

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 Proton–Proton and Proton–Carbon-13 Spin–Spin Coupling Constants in 1,3-Dioxole and Bis-1,3-dioxolyl. Conformational Dependence

1975 ◽  
Vol 53 (18) ◽  
pp. 2734-2741 ◽  
Author(s):  
Ted Schaefer ◽  
Kalvin Chum ◽  
David McKinnon ◽  
M. S. Chauhan
Keyword(s):  
Double Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Dihedral Angles ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton ◽  
Karplus Relationship ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The carbon-13 satellite peaks in the proton magnetic resonance spectra of 1,3-dioxole and bis-1,3-dioxolyl are analyzed under single and double resonance conditions to yield the signs and magnitudes of proton–proton coupling constants over three, four, and five bonds, and of proton–carbon-13 coupling constants over one, two, and three bonds. The conformational behavior of bis-1,3-dioxolyl contrasts sharply with that of analogous sym-tetrasubstituted ethane derivatives. It is indicated that the two-bond proton–carbon-13 coupling in the ethanic fragment can be used for conformational analysis in a manner similar to vicinal proton–proton couplings. The vicinal three-bond proton–carbon-13 couplings are given for dihedral angles of 180 and 120° and their relative magnitudes are as expected from a Karplus relationship. The two-bond proton–carbon-13 coupling in the olefinic fragment is, at 20.0 Hz, the largest coupling known for such a bond.

The conformational distribution of 2-cyanobenzaldehyde and 3-cyanobenzaldehyde in solution and in the vapor

1991 ◽  
Vol 69 (7) ◽  
pp. 1039-1046 ◽  
Author(s):  
Ted Schaefer ◽  
Kerry J. Cox ◽  
Rudy Sebastian
Keyword(s):  
Long Range ◽  
Dipole Moments ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Orbital Theory ◽  
Spectral Parameters ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
Spin Spin Coupling

The 1H nuclear magnetic resonance spectra of 2-cyanobenzaldehyde (2CNB) and 3-cyanobenzaldehyde (3CNB) in CS2/C6D12 and acetone-d6 solutions at 300 K yield precise stereospecific long-range proton–proton coupling constants. These are used to establish the conformational population of the o-cis and o-trans conformers of these relatively polar molecules. For example, the fractional o-cis population of 2CNB changes from 0.12(4) in CS2/C6D12 to 0.46(6) in acetone-d6, whereas that of 3CNB is 0.48(2) in both solvents. Extrapolation to the vapor phase, using a dielectric model, implies a negligible concentration of the o-cis conformer of 2CNB and a roughly 50% abundance of each conformer of 3CNB. Computations at various levels of molecular orbital theory provide estimates of the rotational barrier of the aldehyde moiety and confirm the planar structure of each conformer. The geometries of three conformers are given as obtained from the 6-31G MO basis and may be useful to molecular spectroscopists. Theoretical and experimental dipole moments are interpolated to yield estimates of their magnitudes for the four planar conformers. Somewhat less precise 1H nmr spectral parameters (than for the above solutions) are also obtained for dilute solutions in benzene-d6 at 300 K. The conformational distributions based on these parameters are compared with their only other measurement, based on dipolar moments in benzene at 298 K. Good agreement between the results of the two methods is found for 3CNB but not for 2CNB. It is suggested that specific interactions occur between benzene solvent and solute molecules, particularly for 3CNB, for which these interactions stabilize the conformer having a low dipole moment. Remarkable changes in the intraring proton–proton coupling constants occur in going from CS2/C6D12 to acetone-d6 solution. Key words: 2- and 3-cyanobenzaldehyde (2CNB and 3CNB): 1H NMR, conformations, long-range spin–spin coupling constants, MO computations.

Calculation of nuclear spin–spin couplings. VIII. Vicinal proton–proton coupling constants in ethane

1995 ◽  
Vol 103 (15) ◽  
pp. 6597-6600 ◽  
Author(s):  
H. Fukui ◽  
H. Inomata ◽  
T. Baba ◽  
K. Miura ◽  
H. Matsuda
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Molecular orbital theory of nuclear spin coupling constants

1964 ◽  
Vol 8 (1) ◽  
pp. 1-18 ◽  
Author(s):  
J.A. Pople ◽  
D.P. Santry
Keyword(s):  
Molecular Orbital ◽  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Spin Coupling Constants
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