The σ−and π−inductive effects

KATRITZKY, A. R.; Topsom, R. D.

doi:10.1021/ed048p427

Cited by 68 publications

(31 citation statements)

References 21 publications

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“…As seen in Table 6, these chemical shift differences indicate a strong n polarization effect (the relatively small shift for C-4 may be due to the counteracting IS inductive effect of the N(CH,),+ group). This is a particularly interesting observation since n polarization effects are usually regarded as unimportant (32). However, we have obtained corroboratory evidence for 7c polarization effects from the I3C chemical shifts of a large number of phenylalkane derivatives (31).…”

Section: ( B ) Sample Preparations and Recovding Of Spectrasupporting

confidence: 66%

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Hamer¹,

Peat²,

Reynolds³

1973

Can. J. Chem.

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Substituent-induced 'H chemical shifts (S.C.S.) for 19 4-substituted a-methyl-and a-t-butylstyrenes have been determined a t infinite dilution in C6Hl2 and 13C S.C.S. have been determined for 0.4 M solutions in CCI,. S.C.S. are correlated with field and resonance substituent parameters and compared with charge densities determined by C N D 0 / 2 MO calculations. The variation of S.C.S. with the dihedral angle, p, between phenyl and vinyl groups and the overall pattern of S.C.S. can be largely accounted for by a model of substituent effects based on field, resonance, and n polarization effects, with conjugative interactions varying as cos2p. Both I3C chemical shifts and charge densities indicate that the n polarization effect consists of two components: (I) a through-space polarization of the vinyl system by the polar C-X bond and (2) polarization of the entire conjugated styrene n electron system. However, significant deviations are noted for some of the 'H S.C.S. correlations. The CND012 calculations indicate that these deviations are primarily due to electronic effects not predicted by the nlodel outlined above. CNDO/2 calculations for related compounds provide a partial explanation by indicating that the magnitude of the field effect depends upon the nature of the molecular framework. Les deplacelnents chimiques en 'H induits par des substituants (S.C.S.) pour 19 a-niethyl et a-tbutylstyrenes substitues en position 4 out Cte determines a dilution infinie dans le C,HIz; ceux-ci en 13C ont Cte determines en solution 0.4 M dans le CC14. Les diplacements chimiques induits par des substituants sont relies aux parametres de champ et de resonance caracteristiques des substituants et compares avec les densites de charge obtenues par des calculs CNDO/2 MO. La variation dans les deplacements chimiques avec I'angle diedre, p, entre les groupes phenyle et vinyl ainsi que le schema general de ces dkplacements chimiques peuvent tres bien s'interpreter a parlir d'un modele des effets de substituants base sur le champ, la risonance et des effets de polarisation n avec des interactions de conjugaison variant selon le cosZp. Les diplacements chimiques en I3C et les densites de charge indiquent tous les deux, que I'effet de polarisation n possede deux composantes: (I) une polarisation a travers l'espace d u systeme vinylique par la liaison polaire C-X et (2) une polarisation du spsteme d'klectrons n du styrene conjugue en entier. Cependant, des Ccarts notables ont Cte observes pour quelques-unes des correlations dans les dtplacements chimiques en 'H. Les calculs CNDO/2 montrent que ces tcarts sont imputables principalement a des effets electroniques imprevisibles selon le n~odele illustri: precedemment. Les calculs CND012 pour des composCs voisins permettent Line explication partielle en montrant que I'amplitude des effets de champ depend de la nature du squelette molCculaire.[Traduit par le journal]Can. J. Chem.. 51. 915 (1973)

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Section: ( B ) Sample Preparations and Recovding Of Spectrasupporting

confidence: 66%

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Hamer¹,

Peat²,

Reynolds³

1973

Can. J. Chem.

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“…In addition, 13C spectra of frans-1-substituted 1,3-butadienes also provide evidence of x polarization effects in these compounds (65). Consequently, we believe that x polarization effects are more important than previously realized (42).…”

Section: (C) Predicted Hrature Of Substituerzt Effects Inmentioning

confidence: 61%

“…TC inductive effects should also affect 6,, and 6,, equally by altering electron density at C-P However, the exact nature of these effects is controversial (42) and further comment will be reserved until section (e).…”

Section: (C) Predicted Hrature Of Substituerzt Effects Inmentioning

confidence: 99%

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. I, 4-Substituted Styrenes

Hamer¹,

Peat²,

Reynolds³

1973

Can. J. Chem.

178

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Correlations of vinyl 'H and 136= chemical shifts and charge densities with field, F, and resonance, R, parameters probide a self-consistent picture of electronic effects in these compounds. 'H chemica! shifts for some derivatives are affected by magnetic effects but this does not obscure the overall pattern of electronic effects. This pattern of electronic effects can be completely accounted for by a nlodel which assumes that substituent effects can be transmitted through space (field effects), via conjugative interactions (resonance effects) or by polarization of the styrene n electron system by the polar C-X bond (n polarization effects). The latter effect appears to be more important than pr-evious!y realized, IH correlations with F and K are used to estimate self-consistent and apparently reasonable values for C=N and C=C-H groups and F a n d R values for carbonyl substituents and (CH3),M sub- Les correlations entre les deplacements chimiques du 'H vinyle et I3C, dcs densites de charge avec le champ F et les parametres de resonance R fournissent une image coherente des effets Clectroniques dans ces con~poses. Dans certains derives les deplacements cliimiques du 'H sont affectis par les effets magnetiques mais cela ne change pas I'allure generale des efTets electroniques qui peut Ctre totalement expliquee par un modele qui suppose que les effets de substituants peuvent etre transmis a travers I'espace (effets de champ), via des interactions de conjugaison (effets de resonance) ou par polarisation du systeme Clectronique du styrene par la liaison C-X (effets de polarisation n). Ce dernier effet est plus important qu'on ne le pensait precCdemmant. Introduction compounds can be accounted for in terms of ziircher (1) and *llinger and coworkers (21, the dipolar electric field effect and the anisohave shown that the substituent dependence of tropic magnetic susceptibility of the substituent.chemical shifts for many aliphatic The substituent dependence of proton chemical shifts (S.C.S.) for aromatic co~npounds is less

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“…This has generally been referred to as a n-inductive effect, although various authors have used the term in different ways (7). The evidence (29)(30)(31) would seem to indicate that the effect does exist; although it is relatively small; however this depends on the sensitivity to n-electron effects of the probe used.…”

Section: Substituent Effects On a Remote N-systemmentioning

confidence: 99%

The Nature and Analysis of Substituent Electronic Effects

Topsom

1976

Progress in Physical Organic Chemistry

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139

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The σ−and π−inductive effects

Abstract: The authors consider, in the absence of the usual terminology or symbols, the possible modes of electric disturbance that can be thought of as contributing to the overall electron distribution.

Cited by 68 publications

References 21 publications

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. I, 4-Substituted Styrenes

The Nature and Analysis of Substituent Electronic Effects

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