Vicinal proton-proton coupling constants V. Couplings to methyl groups

Guilleme, J.; Fabián, J. San

doi:10.1080/002689797171634

Cited by 13 publications

(1 citation statement)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Calculated substituent effects, DJ X , increase when increasing the substituent electronegativity. Substituent effects on 3 J(HH), D 3 J X Me , were also calculated by Guilleme et al (128) (Fig. 15) in monosubstituted and 1,1-disubstituted ethanes, with substituents containing atoms from the 2nd to the 5th rows of the periodic table.…”

Section: Dihedral Anglesmentioning

confidence: 72%

From NMR spectra to structure

Facelli

Ferraro

2013

Concepts Magnetic Resonance

View full text Add to dashboard Cite

This article discusses the existing methods to correlate NMR parameters describing the high resolution NMR spectra of liquids and solid systems with their structural parameters. Those methods are divided into direct and indirect ones. This article includes two types of direct methods: those based on the Nuclear Overhauser Effect (NOE) contributions to the NMR relaxation and those based on direct measurements of the dipolar couplings using several experimental approaches. Indirect methods are based on the intrinsic dependence of J couplings and shieldings on the atomic coordinates of the atoms in a molecule and its surroundings, requiring complex quantum mechanical calculations to relate NMR spectral properties to molecular and crystal structure. This article discusses how changes in chemical bonding, conformation, and stereo configurations that cause measurable changes in NMR parameters closely related to molecular and crystal structure. The final section provides information about the software and hardware required to perform calculations needed to solve structural problems using high resolution NMR. This article intends to provide molecular structural researchers new to the field of NMR, with an overall panorama of the potential of using high resolution NMR for structure elucidation, when other more traditional techniques are not feasible. To this end and to emphasize the didactic value of this work, after each section a brief conclusion has been added to recap the critical concepts. © 2014 Wiley Periodicals, Inc. Concepts Magn Reson Part A 42A: 261–289, 2013.

show abstract

Section: Dihedral Anglesmentioning

confidence: 72%

From NMR spectra to structure

Facelli

Ferraro

2013

Concepts Magnetic Resonance

View full text Add to dashboard Cite

show abstract

NMR ³J(C₁,H₃) couplings in 1‐X‐bicyclo[1.1.1]pentanes. FPT–DFT and NBO studies of hyperconjugative interactions and heavy atom substituent effects

2001

View full text Add to dashboard Cite

ABSTRACT:In this work a rationalization of the very large substituent effects on 3 J(C 1 ,H 3 ) couplings in 1-X-bicyclo[1.1.1]pentanes is presented. The Fermi contact contribution to such couplings was calculated in a series of 13 X-derivatives within the DFT-B3LYP framework using the finite perturbation theory. Core electrons for atoms beyond the Second Row were taken into account using effective core potentials. Calculated couplings are in very good agreement with experimental values. The role played by hyperconjugative interactions involving bonds or antibonds belonging to the coupling pathway are studied using the NBO approach. Heavy atom contribution to substituent effects on 3 J(C 1 ,H 3 ) couplings was estimated as small. This contrasts notably with trends observed in the corresponding 13 C substituent chemical shifts, SCSs. The latter were estimated comparing for X = Cl, Br, I, SnMe 3 , calculated SCSs with their experimental values. Such estimations are in line with explicit calculations of the spin-orbit contribution reported in the literature for smaller compounds.

show abstract

The effect of carbonyl group in the asymmetry of ^{3, 4}J_CH coupling constants in norbornanones

Santos¹,

Tormena²,

Contreras³

et al. 2007

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

A rationalization of the known difference between the 3,4JC4H1 and 3,4JC1H4 couplings transmitted mainly through the 7-bridge in norbornanone is presented in terms of the effects of hyperconjugative interactions involving the carbonyl group. Theoretical and experimental studies of 3,4JCH couplings were carried out in 3-endo- and 3-exo-X-2-norbornanone derivatives (X = Cl, Br) and in exo- and endo-2-noborneol compounds. Hyperconjugative interactions were studied with the natural bond orbital (NBO) method. Hyperconjugative interactions involving the carbonyl pi*(C2=O) and sigma*(C2=O) antibonding orbitals produce a decrease of three-bond contribution to both 3,4JC4H1 and 3,4JC1H4 couplings. However, the latter antibonding orbital also undergoes a strong sigmaC3--C4 --> sigma*(C2=O) interaction, which defines an additional coupling pathway for 3,4JC4H1 but not for 3,4JC1H4. This pathway is similar to that known for homoallylic couplings, the only difference being the nature of the intermediate antibonding orbital; i.e. for 3,4JC4H1 it is of sigma*-type, while in homoallylic couplings it is of pi*-type.

show abstract

Vicinal proton-proton coupling constants V. Couplings to methyl groups

Cited by 13 publications

References 32 publications

From NMR spectra to structure

From NMR spectra to structure

NMR ³J(C₁,H₃) couplings in 1‐X‐bicyclo[1.1.1]pentanes. FPT–DFT and NBO studies of hyperconjugative interactions and heavy atom substituent effects

The effect of carbonyl group in the asymmetry of ^{3, 4}J_CH coupling constants in norbornanones

Contact Info

Product

Resources

About

Vicinal proton-proton coupling constants V. Couplings to methyl groups

Cited by 13 publications

References 32 publications

From NMR spectra to structure

From NMR spectra to structure

NMR 3J(C1,H3) couplings in 1‐X‐bicyclo[1.1.1]pentanes. FPT–DFT and NBO studies of hyperconjugative interactions and heavy atom substituent effects

The effect of carbonyl group in the asymmetry of 3, 4JCH coupling constants in norbornanones

Contact Info

Product

Resources

About

NMR ³J(C₁,H₃) couplings in 1‐X‐bicyclo[1.1.1]pentanes. FPT–DFT and NBO studies of hyperconjugative interactions and heavy atom substituent effects

The effect of carbonyl group in the asymmetry of ^{3, 4}J_CH coupling constants in norbornanones