Valence bond studies of internuclear coupling

Gutowsky, H. S.; Juan, Cynthia

doi:10.1039/df9623400052

Cited by 32 publications

(1 citation statement)

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“…Most work on this subject has been based on an observed proportionality between the 13C-H coupling constants (JcH) of simple hydrocarbons and the s character of the carbon hybrid orbital directed to the proton, the type of hybridization considered being sp 3, sp 2 and sp, respectively for saturated, olefinic and acetylenic carbon atoms [1,2]. For substituted hydrocarbons, the fact that Jc~ usually increases as the electronegativity of the other atoms bonded to C increases has then been ascribed chiefly to a change of hybridization of the carbon atom, with an increase of s character in the CH bond in question [3,4].…”

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confidence: 99%

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

Gil¹,

Teixeira‐Dias²

1968

Molecular Physics

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The effect of substituents on 13C-H coupling constants is discussed, within the framework of the Pople-Santry MO theory of nuclear spin coupling, by making a theoretical analysis of the contributions due to differences of coulomb and resonance integrals as well as due to the presence of electron lone-pairs.Earlier treatments based on correlations of dcrt with s characters are shown to be less justified mainly because the description of CH bonds in terms of localized MO's is not valid, and no physical meaning can be rigorously attributed to concepts such as rehybridization.

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confidence: 99%

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

Gil¹,

Teixeira‐Dias²

1968

Molecular Physics

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Indirect Coupling: Theory and Applications in Organic Chemistry

Barfield

2007

Encyclopedia of Magnetic Resonance

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The influence of spatial orientation of free orbitals in pmr spectroscopy influence of vicinal orbitals on³J and²J

Anteunis¹

1966

Bulletin des Soc Chimique

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In accordance with recent literature data, it is proposed that an increment of + 2.3 cps and + 1.8 cps is to be added to the vicinal PJ) and gem (2J) coupling values respectively, each time an a-oxygen (or a-nitrogen) atom has one of its free electron pair p-orbitals parallel with the carbon hydrogen bond of one of the protons involved in the coupling under consideration. An influence on 3J coupling values in three membered rings (epoxides) is however not to be considered. Molecular deformations which disturb the parallelity (i.e. in the rigid half chair form of pentacyclic compounds or in the twist form of hexacyclic compounds) nullify this effect. The Karplus rule and the electronegativity rule have regained a great amount of their reliability with this supplementary effect.The generalised deduction that electronegative substitution causes a marked algebraic decrease of the vicinal and geminal coupling constants ( I ) has been controversed recently (').There is indeed an increasing amount of data which is in contradiction with these electronegativity rules. On the other hand it is also a fact that the so valuable "Karplus" effect (3) is often incapable to explain observed coupling values. This creates difficulties in evaluating molecular shapes and conformational data. Unfortunately the deviations seem to be greatest in cyclic compounds with more or less rigid structure, which are of the most fundamental character, (l) J.R.

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Valence bond studies of internuclear coupling

Cited by 32 publications

References 9 publications

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

Indirect Coupling: Theory and Applications in Organic Chemistry

The influence of spatial orientation of free orbitals in pmr spectroscopy influence of vicinal orbitals on³J and²J

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Valence bond studies of internuclear coupling

Cited by 32 publications

References 9 publications

Molecular orbital calculations of substituent effects on directly bonded13C-H coupling constants

Molecular orbital calculations of substituent effects on directly bonded13C-H coupling constants

Indirect Coupling: Theory and Applications in Organic Chemistry

The influence of spatial orientation of free orbitals in pmr spectroscopy influence of vicinal orbitals on3J and2J

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About

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

Molecular orbital calculations of substituent effects on directly bonded¹³C-H coupling constants

The influence of spatial orientation of free orbitals in pmr spectroscopy influence of vicinal orbitals on³J and²J