High resolution carbon-13 nuclear magnetic resonance spectra including long-range 13CH coupling constants for symmetrical meta-dihalobenzenes

High-resolution spectra have been obtained from the hydrogen nuclei of appropriate isotopic mixtures of ethane, ethylene and acetylene containing one or two magnetic 13 C nuclei. Analysis of these spectra has yielded the magnitudes of all but one of the possible inter - nuclear coupling constants in these molecules, including those between pairs of carbon nuclei. Where a given molecule has several coupling constants between pairs of the same type of nuclei the relative signs of these have also been determined. Discussion of the experimental results in terms of current theoretical treatments shows that in nearly all cases the contact, H 3 , term is the most important one in determining the magnitude of the coupling constants. Only in the case of the J CC and the long-range J ' CH coupling constants of acetylene does it appear to be necessary to consider appreciable contributions from other terms.

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High-resolution nuclear-magnetic-resonance spectra of hydrocarbon groupings - V. ABCX spectra of vinyl fluoride and 3-methylbut-l-ene

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1961.0152 ◽

1961 ◽

Vol 263 (1312) ◽

pp. 136-148 ◽

Cited By ~ 27

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

High Resolution ◽

Coupling Constants ◽

Vinyl Fluoride ◽

General Properties ◽

Nuclear Magnetic Resonance Spectra ◽

Magnetic Resonance Spectra ◽

Nuclear Magnetic

Some general properties of ABCX -type spectra are discussed. It is shown that it is possible to deduce from such spectra the relative signs of all inter-nuclear coupling constants. Analyses are presented of the hydrogen (proton) spectra from the vinyl groups of vinyl fluoride and 3-methylbut-l-ene, and of the fluorine spectrum of the former molecule. It is shown that all HF coupling constants in vinyl fluoride are of the same sign as the cis and trans HH coupling constants.

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

Canadian Journal of Chemistry ◽

10.1139/v88-101 ◽

1988 ◽

Vol 66 (4) ◽

pp. 584-590 ◽

Cited By ~ 8

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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