Geschwindigkeitskonstanten für den Angriff von Carbenium‐Ionen an Arene — eine Brücke zwischen der Chemie aliphatischer und aromatischer π‐Systeme

Mayr, Herbert; Bartl, J.; Hagen, G.

doi:10.1002/ange.19921041241

Cited by 24 publications

(4 citation statements)

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“…In some cases (slight) deviations from the second-order rate law after two half-lifes were observed. If the attack of 2 + at 1 were reversible, the reactions should proceed faster at higher concentrations of the counterions which behave as bases 5b.…”

Section: Resultsmentioning

confidence: 99%

“…Only recently, the first absolute rate constants for the attack of carbocations at arenes have been reported, and it has been shown that these reactions follow the linear free enthalpy relationship (eq 2), where E represents the strength of the electrophiles, while N and s characterize the nucleophiles' reactivity . Since N and s parameters have also been determined for nonaromatic π-systems, a direct comparison of the nucleophilic reactivities of substituted benzenes, alkenes, and other π-nucleophiles became possible.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

and

Mayr

1998

J. Org. Chem.

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The kinetics of the reactions of benzhydryl cations with heteroarenes (N-methylpyrrole, furan, 2-methylfuran, and 2-methylthiophene) have been determined photometrically in dichloromethane, and the reaction products have been completely characterized by 1H and 13C NMR spectroscopy. The reactions follow second-order kinetics with rate-limiting formation of the σ-adducts. The second-order rate constants correlate linearly with the electrophilicity parameter E of the benzhydryl cations. This allows the determination of the reactivity parameters N and s for the heteroarenes according to the linear free enthalpy relationship log k = s(E + N) (Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938−957). The nucleophilicity parameters N thus defined allow a direct comparison of the nucleophilic reactivities of aromatic and nonaromatic π-systems. Since N correlates linearly with σ+ arene, it becomes possible to derive N parameters for arenes and heteroarenes with known σ+ parameters and to calculate absolute rate constants for their reactions with carbenium ions and diazonium ions. Applications of the reactivity parameters thus determined for the quantitative and qualitative prediction of the rates of electrophilic aromatic substitutions are discussed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

and

Mayr

1998

J. Org. Chem.

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“…Auch Reaktionen von Diarylcarbenium-Ionen mit Benzolde rivaten (Tabelle 6) weisen eine komplexe Kinetik auf [38] …”

Section: Nucleophilie-und Elektrophilieskalenunclassified

Nucleophilie‐ und Elektrophilieskalen als Ordnungsprinzipien polarer organischer und metallorganischer Reaktionen

1994

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“…Correlation Analysis for the Basis Set Compounds. Table lists 209 rate constants for the reactions of 23 benzhydrylium ions with 38 π-nucleophiles, − 87 of which have not been published previously. It is a complete collection of all presently available rate constants for reaction series consisting of a benzhydrylium ion with three or more π-nucleophiles.…”

Section: Introductionmentioning

confidence: 99%

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles^,

et al. 2001

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Twenty-three diarylcarbenium ions and 38 pi-systems (arenes, alkenes, allyl silanes and stannanes, silyl enol ethers, silyl ketene acetals, and enamines) have been defined as basis sets for establishing general reactivity scales for electrophiles and nucleophiles. The rate constants of 209 combinations of these benzhydrylium ions and pi-nucleophiles, 85 of which are first presented in this article, have been subjected to a correlation analysis to determine the electrophilicity parameters E and the nucleophilicity parameters N and s as defined by the equation log k(20 degrees C) = s(N + E) (Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938-957). Though the reactivity scales thus obtained cover more than 16 orders of magnitude, the individual rate constants are reproduced with a standard deviation of a factor of 1.19 (Table 1). It is shown that the reactivity parameters thus derived from the reactions of diarylcarbenium ions with pi-nucleophiles (Figure 3) are also suitable for characterizing the nucleophilic reactivities of alkynes, metal-pi-complexes, and hydride donors (Table 2) and for characterizing the electrophilic reactivities of heterosubstituted and metal-coordinated carbenium ions (Table 3). The reactivity parameters in Figure 3 are, therefore, recommended for the characterization of any new electrophiles and nucleophiles in the reactivity range covered. The linear correlation between the electrophilicity parameters E of benzhydryl cations and the corresponding substituent constants sigma(+) provides Hammett sigma(+) constants for 10 substituents from -1.19 to -2.11, i.e., in a range with only very few previous entries.

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Geschwindigkeitskonstanten für den Angriff von Carbenium‐Ionen an Arene — eine Brücke zwischen der Chemie aliphatischer und aromatischer π‐Systeme

Cited by 24 publications

References 22 publications

Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

Nucleophilie‐ und Elektrophilieskalen als Ordnungsprinzipien polarer organischer und metallorganischer Reaktionen

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles^,

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Geschwindigkeitskonstanten für den Angriff von Carbenium‐Ionen an Arene — eine Brücke zwischen der Chemie aliphatischer und aromatischer π‐Systeme

Cited by 24 publications

References 22 publications

Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

Kinetics of the Friedel−Crafts Alkylations of Heterocyclic Arenes: Comparison of the Nucleophilic Reactivities of Aromatic and Nonaromatic π-Systems

Nucleophilie‐ und Elektrophilieskalen als Ordnungsprinzipien polarer organischer und metallorganischer Reaktionen

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles,

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Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles^,