The analysis of the nuclear magnetic resonance spectra of some saturated and unsaturated hydrocarbon groupings

Banwell, C.N.; Sheppard, N.; Turner, James J.

doi:10.1016/0371-1951(60)80026-4

Cited by 35 publications

(7 citation statements)

References 11 publications

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“…In considering the effect of substituent electronegativity on the long-range coupling constant, an analogy may be drawn with the couplings in vinyl derivatives 23 and in their adducts with perchloro-cyclopentadiene. 18 In both of these cases, the slope of the plot of coupling constant against electronegativity of the attached group is roughly the same for all three coupling constants, and is independent of the absolute magnitude of the constant ; thus the gem coupling constant in vinyl derivatives varies from about -2 to + 2 c/sec as the substituent group is changed from -F to -C = .…”

Section: Discussionmentioning

confidence: 99%

Rotational isomerism about single bonds in olefinic compounds

Bothner‐By¹,

Günther²

1962

Discuss. Faraday Soc.

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Analysis of the 60 Mc/sec high resolution proton n.m.r. spectra of samples of allyl chloride, allyl bromide, allyl iodide and allyl benzene both neat and in 10 % (viv) solution in CC14 yield sets of coupling constants and chemical shifts from which conclusions may be drawn concerning the relative stabilities of the rotational conformers. In allyl chloride and ally1 benzene that conformer with the substituent gauche to the proton on trigonai carbon is slightly preferred. The preference for this conformer becomes increasingly more pronounced in allyl bromide and allyl iodide.Numerous studies 1-9 have been directed at establishing the nature of rotational isomerism about the single bond joining trigonal carbon to tetrahedral carbon. It now appears reasonably certain that in many compounds the stable conformations are those derivable from the conformation (la) established for acetaldehyde 5 and propene 6 by means of microwave spectroscopy. The rotamers of monosubstituted propenes may thus be depicted as (lb), (lc) and (lc').High resolution n.m.r. has proven a useful tool in exploring rotarner equilibria and rates of interconversion in unsaturated 8,9 and saturated 10-12 systems. Its application rests on the theoretically predicted 13 and experimentally observed 14 dependence of proton-proton spin coupling constant on H 4 -C -H dihedral angle. This dependence appears to be of essentially the same form whether the adjacent protons are both on tetrahedral carbon, or whether they are on adjoining tetrahedral and trigonal carbons.15The purpose of the present work is to explore the application of this tool to the study of rotamerism in other allylic compounds, namely allyl chloride, allyl bromide, allyl iodide and allyl benzene. EXPERIMENTAL MATERIALSSamples of coinmercial provenance were purified by distillation and gas chromatography (VPC). VPC showed no detectable impurities in the purified allyl chloride and allyl bromide, 0.6 % of unidentified material in allyl benzene, and 1-7 % unidentified material in allyl iodide which, however, could not be removed by further distillation, and presumably represented thermal decomposition products of the allyl iodide. CCb was commercial reagent grade, and showed no impurities detectable by VPC.Samples (pure, or in 10 % v/v solution in CCb) were introduced into precision ground 5 mm cells and degassed on the vacuum line ; 3 % (v/v) of tetramethylsilane was added ;

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Section: Discussionmentioning

confidence: 99%

Rotational isomerism about single bonds in olefinic compounds

Bothner‐By¹,

Günther²

1962

Discuss. Faraday Soc.

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“…All coupling constants are positive [15]. Downloaded by [McGill University Library] at 10:08 18 November 2014 coupling constants [23,24,[26][27][28][29][30]. The results are summarized in table 9.…”

Section: Spectramentioning

confidence: 99%

Proton magnetic resonance of symmetrical molecules

1964

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“…Therefore, one can seek to derive eqn. (6) on the basis of hybridization and/or polarity changes produced in the C-H bond by the substituent. Or one can investigate the other contributions, such as n-electron and orbital polarization terms, which X could make to JCH without affecting materially the C-H bond.…”

Section: Effects Of Substituents U P O N Jchmentioning

confidence: 99%

“…JcH(CHXYZ) = JcH(CH4) + + 6, + 6z. (6) ag(CHXYZ) = ($)(I +Ax+Ay+Az)-Ax. (21) and for CHXYZ, By means of eqn.…”

Section: Valence B O N D Formulation For Jchmentioning

confidence: 99%

“…Usually, only the magnitudes of J have been obtained from experiment; but increasing attention is being given to the importance of their relative signs. Several substituted ethylenes have been reported 5 9 6 in which the sign of JZE (1 to 3 c/sec) is opposite to, and also the same as, that of JzF (5 to 11 c/sec) and J t s s (12 to 18 clsec). These results are compatible with the valence-bond calculations for the CH2 fragment,s which neglect substituent and n-electron effects, and which predict that JgE should become negative for HCH bond angles larger than about 120°.53 7 Similarly, there are substituted ethanes in which the sign of the vicinal coupling JF (1 to 3 c/sec) is opposite to and also the same as, that ofJFH (10 to 16-5 c/sec).49 6 Again, the results seem compatible with the calculated dependence of the coupling upon the dihedral angle 4, because substituent effects were neglected and tetrahedral HCC angles were assumed.3…”

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confidence: 96%

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