Über Cyclo‐octatetraen

Willstätter, Richard; Waser, E.

doi:10.1002/cber.191104403216

Cited by 169 publications

(98 citation statements)

References 14 publications

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“…176 The C60 n-(n > 0) was taken as a model for the cage of endohedral metallofullerenes. It was found that the reaction becomes more exothermic (and the barrier is reduced) for the [5,6] attack when n increases from 0 to 6 electrons (see Fig. 5).…”

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 92%

“…5). On the other hand, for the [6,6] addition the exothermicity is somewhat reduced (and the barrier increases) when n increases. For n = 4-5, there is a change in the regioselectivity of the process and the [5,6] becomes the preferred attack.…”

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 97%

“…( , ) = 2 ∑ ( ) ( ) (6) where the summations run over all the pairs of occupied spin molecular orbitals (MO) of the molecule. The Sij(A) terms in Eqs.…”

Section: How Can Electronic Delocalisation Be Measured?mentioning

confidence: 99%

“…The reactivity and regioselectivity of Diels-Alder (DA) reaction involving empty fullerenes is generally favoured for [6,6] bonds, whereas in endohedral metallofullerenes [5,6] bonds are commonly more reactive. 175,176 When a metal cluster is encapsulated inside a fullerene there is a charge transfer from the metal cluster to the fullerene.…”

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 99%

“…In the case of M3N units (M = Sc, Y, Gd…) formally six electrons are transferred to the carbon cage. We decided to analyse the effect of adding electrons to the fullerene cage by calculating the reaction profile for the DA reaction of cyclopentadiene (Cp) to the [6,6] and [5,6] bonds of C60 n-(n = 0 -6) species. 176 The C60 n-(n > 0) was taken as a model for the cage of endohedral metallofullerenes.…”

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 99%

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Quantifying aromaticity with electron delocalisation measures

et al. 2015

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Aromaticity cannot be measured directly by any physical or chemical experiment because it is not a well-defined magnitude. Its quantification is done indirectly from the measure of different properties that are usually found in aromatic compounds such as bond length equalisation, energetic stabilisation, and particular magnetic behaviour associated with induced ring currents. These properties have been used to set up the myriad of structural-, energetic-and magnetic-based indices of aromaticity known to date. Cyclic delocalisation of mobile electrons in two or three dimensions is probably one of the key aspects that characterise aromatic compounds. However, it has not been until the last decade that electron delocalisation measures have been widely employed to quantify aromaticity. Some of these new indicators of aromaticity such as the PDI, FLU, ING, and INB were defined in our group. In this paper, we review the different existent descriptors of aromaticity that are based on electron delocalisation properties, we compare their performance with indices based on other properties, and we summarise a number of applications of electronic-based indices for the analysis of aromaticity in interesting chemical problems.2

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Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 92%

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 97%

“…( , ) = 2 ∑ ( ) ( ) (6) where the summations run over all the pairs of occupied spin molecular orbitals (MO) of the molecule. The Sij(A) terms in Eqs.…”

Section: How Can Electronic Delocalisation Be Measured?mentioning

confidence: 99%

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 99%

Section: Aromaticity Determines the Regioselectivity Of Diels-alder Rmentioning

confidence: 99%

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Quantifying aromaticity with electron delocalisation measures

et al. 2015

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Ylidische viergliedrige Vier-π-Elektronen-λ5-Phosphorheterocyclen: elektronische Heterocyclobutadien-Isomere

Bertrand

1998

Angewandte Chemie

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Ausgebootet: Dem etablierten Konzept der Antiaromatizität von Hückel spielen Phosphorheterocyclen einen Streich. Zwar liegt sowohl zwischen der Entdeckung von Benzol und der von Cyclobutadien als auch zwischen der ersten Synthese von Hexachlorcyclotriphosphazen 1 und Heterocyclen des Typs 2 jeweils ein Zeitraum von mehr als einem Jahrhundert – doch damit hört die Analogie auf: Die Derivate von 2 sind wie Cyclobutadiene viergliedrige Vier‐π‐Elektronen‐Ringsysteme, aber nicht antiaromatisch!

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Powerful Oxidizing Properties of a Planar [8]Annulene: Tetrakis(perfluorocyclobuta)cyclooctatetraene and Its Radical Anion

Gerson¹,

Huber²,

Merstetter³

et al. 1999

HCA

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The central eight‐membered ring of tetrakis(perfluorocyclobuta)cyclooctatetraene (1) is flat both in the crystal and in solution, but tetrakis(perfluorocyclopenta)cyclooctatetraene (2) assumes a tub shape similar to that of parent cyclooctatetraene. This sterically induced structural difference strongly affects the physical properties of compounds 1 and 2. The first and second reduction potentials of 1 in solution, +0.79 and +0.14 V vs. SCE, are considerably more positive than the corresponding values, +0.20 and −0.21 V, of 2. Accordingly, mere contact with Hg metal in N,N‐dimethylformamide converts 1 to an unusually stable radical anion 1.− that is persistent in air. The temperature‐independent coupling constant, aF=+0.320 mT, of the sixteen equivalent β‐19F‐nuclei in 1.− is much smaller than the expected value, and the g factor of 1.− is markedly lower than those generally found for structurally related radical anions. In contrast, the characteristic data for 2.−, generated from 2 with K metal in 1,2‐dimethoxyethane, comply with the expected data. The coupling constants aF=+0.976 and +0.935 mT, each of eight β‐19F‐nuclei in 2.−, average +0.951 mT upon raising the temperature from 220 to 260 K. The gas‐phase electron affinity of 1, A=3.4±0.2 eV, which was estimated from the reduction potential in solution and from charge‐transfer absorption spectra obtained from a series of methylated benzenes and naphthalenes, is among the highest known for neutral organic molecules.

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Über Cyclo‐octatetraen

Cited by 169 publications

References 14 publications

Quantifying aromaticity with electron delocalisation measures

Quantifying aromaticity with electron delocalisation measures

Ylidische viergliedrige Vier-π-Elektronen-λ5-Phosphorheterocyclen: elektronische Heterocyclobutadien-Isomere

Powerful Oxidizing Properties of a Planar [8]Annulene: Tetrakis(perfluorocyclobuta)cyclooctatetraene and Its Radical Anion

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