Signs and mechanisms of 13C, 19F spin–spin coupling constants in benzotrifluoride and its derivatives

1983 ◽  
Vol 61 (12) ◽  
pp. 2779-2784 ◽  
Author(s):  
Ted Schaefer ◽  
Kirk Marat ◽  
James Peeling ◽  
Richard P. Veregin
Keyword(s):  
Long Range ◽  
Spin State ◽  
Nuclear Spin ◽  
Opposite Sign ◽  
Coupling Constants ◽  
Spin Coupling ◽  
State Information ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The magnitudes of nJ(C, F) for n = 3, 4, 5 bonds are remeasured for benzotrifluoride. The signs of 2J(C, F) and 3J(C, F) are determined for 4-chloro-3,5-dinitrobenzotrifluoride and that of 5J(C, F) for 2-amino-3,5-dibromobenzotrifluoride. 4J(C, F) is not observable in these compounds. The contact contributions to nJ(C, F) are calculated for benzotrifluoride by INDO MO FPT. The long-range coupling constants are discussed in terms of the mechanisms which transmit nuclear spin state information. It seems that 5J(C, F) is a σ–π coupling, 4J(C, F) is a composite of a and σ–π components of opposite sign, and that 3J(C, F) has a Karplus behaviour modified by a σ–π contribution.

The carbonyl group as a reluctant transmitter of hyperconjugative or σ–π spin–spin coupling interactions in derivatives of benzaldehyde, acetophenone, and benzophenone

1986 ◽  
Vol 64 (9) ◽  
pp. 1859-1863 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Glenn H. Penner ◽  
Alberta Lemire ◽  
Reino Laatikainen
Keyword(s):  
Opposite Sign ◽  
Coupling Constants ◽  
The Other ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
State Information ◽  
Spin Polarizability ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

Unlike their counterparts in anisole or toluene derivatives, the six-bond spin–spin coupling constants between para ring protons or 19F nuclei and protons or 13C nuclei in the sidechain of derivatives of benzaldehyde, acetophenone, and benzophenone can apparently contain components of opposite sign, at least for the fluorine derivatives. The σ–π components are much smaller in magnitude than in toluene derivatives, leading to very small or unobservable coupling constants. Consequently they are of limited use in conformational analysis. INDO MO FPT computations and their modifications are examined as to the reasons for the small σ–π magnitudes. Although the spin polarizability of the 2pz orbital on oxygen appears to play an important role in the transmission of nuclear spin state information, the computations do not account for a 19F coupling mechanism that appears to be significant for planar conformations. On the other hand, spin–spin coupling constants over five formal bonds to meta protons are sizeable and stereospecific.

Vibrational and thermal averaging of the indirect nuclear spin-spin coupling constants of CH4, SiH4, GeH4 and SnH4

1997 ◽  
Vol 91 (5) ◽  
pp. 897-907 ◽  
Author(s):  
SHEELA KIRPEKAR ◽  
THOMAS ENEVOLDSEN ◽  
JENS ODDERSHEDE ◽  
WILLIAM RAYNES
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

High‐Level Electron Correlation of the Indirect Nuclear Spin‐Spin Coupling Constants in Some Small Diboranes and Lithium‐Doped Diboranes

2021 ◽  
Vol 6 (22) ◽  
pp. 5451-5465
Author(s):  
Antonio P. Santos Neto ◽  
Roberto Rivelino ◽  
Gabriel I. Pagola ◽  
Patricio F. Provasi
Keyword(s):  
Electron Correlation ◽  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
High Level ◽  
Spin Spin Coupling

Geminal tin-tin indirect nuclear spin-spin coupling constants in some trimethyl tin group IV and group V compounds

1981 ◽  
Vol 44 (1) ◽  
pp. 54-61 ◽  
Author(s):  
W Biffar ◽  
T Gasparis-ebeling ◽  
H Nöth ◽  
W Storch ◽  
B Wrackmeyer
Keyword(s):  
Nuclear Spin ◽  
Group Iv ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Group V ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

scholarly journals Proximity Effects on Nuclear Spin-Spin Coupling Constants. 1. J(CH) Couplings in the Vicinity of an Atom Bearing Lone Pairs

1994 ◽  
Vol 98 (36) ◽  
pp. 8858-8861 ◽  
Author(s):  
C. Vizioli ◽  
M. C. Ruiz de Azua ◽  
C. G. Giribet ◽  
R. H. Contreras ◽  
L. Turi ◽  
...  
Keyword(s):  
Nuclear Spin ◽  
Proximity Effects ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Lone Pairs ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

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.

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