Guido Vanermen

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Paul Geerlings

Vrije Universiteit Brussel

Marcel Van Beylen

KU Leuven

Suzanne Toppet

KU Leuven

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KU Leuven

UCLouvain

Vrije Universiteit Brussel

Ghent University

Vrije Universiteit Amsterdam

University of Girona

Universidad Andrés Bello

Pontificia Universidad Católica de Chile

Research Foundation - Flanders

McMaster University

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Dissociation behavior of benzylalkali compounds in tetrahydrofuran: effect of countercation, aromatic methoxy substitution, and .alpha.-alkyl substitution

The Journal of Physical Chemistry (1986)

Guido Vanermen Marcel Van Beylen Paul Geerlings

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDissociation behavior of benzylalkali compounds in tetrahydrofuran: effect of countercation, aromatic methoxy substitution, and .alpha.-alkyl substitutionG. Vanermen, M. Van Beylen, and P. GeerlingsCite this: J. Phys. Chem. 1986, 90, 4, 603–607Publication Date (Print):February 1, 1986Publication History Published online1 May 2002Published inissue 1 February 1986https://pubs.acs.org/doi/10.1021/j100276a024https://doi.org/10.1021/j100276a024research-articleACS PublicationsRequest reuse permissionsArticle Views311Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Tetrahydrofuran

Substitution (logic)

Electrophilic aromatic substitution

10.1021/j100276a024

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Citations (7)

Quantum chemical calculations and nuclear magnetic resonance measurements on benzyl-type carbanions. II: Influence of countercations and interacting unsaturated systems

Journal of The Chemical Society-perkin Transactions 1 (1986)

Guido Vanermen Suzanne Toppet Marcel Van Beylen Paul Geerlings

Carbanion

Source

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Quantumchemical Calculations and NMR Measurements on Benzyl-type carbanions. Part I : The Effect of an aromatic CH3O-substituent. (Resonance Saturation) and a-alkyl substitution

Guido Vanermen Marcel Van Beylen Suzanne Toppet Paul Geerlings

Carbanion

Saturation (graph theory)

Substitution (logic)

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Quantum chemical calculations and nuclear magnetic resonance measurements on benzyl-type carbanions. Part 1. The effect of an aromatic methoxy substituent (resonance saturation) and α-alkyl substitution

Journal of the Chemical Society. Perkin transactions II (1986)

Guido Vanermen Suzanne Toppet Marcel Van Beylen Paul Geerlings

Ab initio STO-3G quantum chemical calculations are reported for benzyl-type carbanions. The influence of aromatic ring substitution by a methoxy group (ortho or para) and of α-alkyl substitution on the electronic properties of the carbanions are investigated. Energetics (e.g. the energy difference between perpendicular and parallel methoxy group conformations, substituent interaction energies) and charge distributions (e.g. total and π-electronic charge excess on the aromatic ring carbons, negative charge excess on the methoxy group) reveal the importance of a resonance saturation effect in these systems due to the simultaneous presence of two π-electron-donating substituents in the aromatic nucleus, the effect being always larger in the case of para-substitution. Upon introduction of an α-alkyl substituent sp2-hybridization is still more favoured and a negative charge transfer to the alkyl group, which acts as an inductive acceptor, occurs. The charge distribution in the aromatic nucleus is hardly changed when compared with the α-unsubstituted case. The 13C and 1H n.m.r. chemical shifts of the benzyl-potassium compounds generally correlate well with the calculated charge distribution in the anions. The non-additivity of the π-electron-donating CH2– and CH3O substituents also shows up in the 13C shift data, the effect again being larger for para than for ortho substitution. When analysing the effect of α-alkyl substitution, a small polarizing effect due to the presence of the countercation should probably be taken into account.

Carbanion

Chemical shift

Electronic effect

10.1039/p29860000699

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Citations (13)

ChemInform Abstract: Quantum Chemical Calculations and NMR Measurements on Benzyl-type Carbanions. Part 2. Influence of Countercations and Interacting Unsaturated Systems

Chemischer Informationsdienst (1986)

Guido Vanermen Suzanne Toppet Marcel Van Beylen Paul Geerlings

Carbanion

10.1002/chin.198636057

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Quantum chemical calculations and nuclear magnetic resonance measurements on benzyl-type carbanions. Part 2. Influence of countercations and interacting unsaturated systems

Journal of the Chemical Society. Perkin transactions II (1986)

Guido Vanermen Suzanne Toppet Marcel Van Beylen Paul Geerlings

Quantum chemical calculations, n.m.r. and spectrophotometric measurements are carried out to study the influence of countercations and interacting unsaturated systems on the structural and electronic properties of benzyl-type carbanions. The calculated geometry of benzyl-Li compares favourably with X-ray data on a related structure. 13C, 1H n.m.r. shifts and 1JCH coupling constants of benzyl, o- and p-CH3O-benzyl-Li, -Na, and -K compounds show a fair overall agreement with the ab initio-calculated charge distributions and structural parameters for the terminal members of the Li-, Na-, and K- series, the Li compound and the free carbanion, modelling the K salt. Both theory and experiment indicate that, when passing from the anion to the alkali-metal compound, an important destruction of the resonance saturation, present in the CH3O derivatives, occurs due to the presence of the countercation, the reduction being more important with decreasing cation radius. The n.m.r. data for α-alkyl-substituted compounds suggest that steric factors make the position of the cation in the Cα region less favourable, the effect being more pronounced for larger cation radius. The resonance saturation effect in the above mentioned systems may also be influenced by intermolecular effects, e.g. it may change during a chemical reaction. Ab initio calculations on the interaction energy between the benzyl-type carbanions and unsaturated systems showing increasing delocalization possibilities for incoming negative charge indicate that the larger this delocalization possibility (ethene < butadiene < styrene), the more important the destruction of resonance saturation. Along this series the parallel conformation of the CH3O group in the p-CH3O compounds gradually becomes less disfavoured. The calculated effect is however not strong enough yet in order to show full agreement with the observed increase in the k(–) value for the addition reaction to 1,1-diphenylethene when passing from polystyryl to poly-p-methoxystyryl carbanions. Larger basis sets and extensive geometry optimization should be carried out in order to settle this problem.

Carbanion

Saturation (graph theory)

Chemical shift

10.1039/p29860000707

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Citations (12)

ChemInform Abstract: Quantum Chemical Calculations and NMR Measurements of Benzyl-type Carbanions.

Chemischer Informationsdienst (1986)

Guido Vanermen Suzanne Toppet Marcel Van Beylen Paul Geerlings

Carbanion

10.1002/chin.198636056

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Citations (0)