Benzvalene, the Tricyclic Valence Isomer of Benzene

Wilzbach, K. E.; Ritscher, James S.; Kaplan, Louis

doi:10.1021/ja00980a053

Cited by 155 publications

(59 citation statements)

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“…2 In 1966, in order to better classify all these isomers, Romanian chemist Balaban defined an interesting new type of isomeric relationship that he named ''valence isomerism. '' 3 Valence isomers of benzene were described by the formula (CH) 6 , each carbon bearing a single hydrogen. In other words, valence isomers of benzene differ only by the ways in which carbon-carbon single and/or double bonds connect six CH units.…”

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confidence: 99%

“…This compound features PBPB cores strongly deviating from planarity (interflap angle between the two PBB units 120.7 and 123. 6 ), short B-B bond lengths (1.875 and 1.906 Å ), and the phenyl linker perpendicular to the PBPB skeletons. The striking differences observed between the solid-state structures of these two derivatives, in addition to a colorless bis(bicyclo[1.1.0]butane), and a deep violet tetraradical, have been explained by a weak ''communication'' between both diradical sites through the antiferromagnetic linker.…”

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confidence: 99%

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Let’s Play with Valence Isomers: The Influence of Different Main Group Elements on Their Relative Stability

Soleilhavoup¹,

Bertrand²

2007

Bulletin of the Chemical Society of Japan

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Valence isomers are compounds featuring the same fragments connected in different ways. In this personal account, we describe how we first met by serendipity this kind of isomerism, and how later on we used the specific properties of phosphorus and boron to prepare two types of valence isomers that are not accessible with elements exclusively from the first long row. In the carbon series, benzene is calculated to be 608 kJ mol À1 lower in energy than its singlet diradical valence isomer, the anti-tricyclohexylene, but a tetraphosphorus analogue of the latter has been isolated. According to calculations, the parent amidinium salt is 541 kJ mol À1 more stable than its three-membered heterocyclic valence isomer, but in the phosphorus series, the difference in energy between the open and closed forms is only a few kJ mol À1 ; provided the right substituents are used, the cyclic form can be isolated. Lastly, among butadiene valence isomers, singlet cyclobutane-1,3-diyls were predicted only as transition states for the inversion of bicyclo[1.1.0]butane. In marked contrast, 1,3-dibora-2,4-diphosphacyclobutane-1,3-diyls can be prepared by valence isomerization of the corresponding butadiene derivatives and isolated under conventional experimental conditions.

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confidence: 99%

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confidence: 99%

Let’s Play with Valence Isomers: The Influence of Different Main Group Elements on Their Relative Stability

Soleilhavoup¹,

Bertrand²

2007

Bulletin of the Chemical Society of Japan

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“…The first six are topologically possible valence isomers of (CH) 6 . [17][18][19][20][21][22] Two non-planar and one planar six-membered rings are theoretically found ones in P 6 23) and in anionic silicon clusters, 8) respectively. Ab initio molecular orbital and density functional theory (DFT) calculations were performed using the Gaussian03 software package.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Theoretical Investigation of Stable Structures of Ge<SUB>6</SUB> Clusters with Various Negative Charges

Kikuchi

Takahashi

2006

Mater. Trans.

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“…This mechanism received strong support by the isolation of benzvalene from the photolysis of benzene (4) and by the formation of bicyclo[3.1.0]hexenyl derivatives (eq. [3]) for benzene-d 6 in 2,2,2-trifluoroethanol (TFE) on photolysis in alcohol solvents (5,6).…”

Section: Introductionmentioning

confidence: 99%

“…The results indicated that these compounds are divided into two independent triads as shown in eqs. [4] and [5]. For instance, photolysis of 9-34 in AN gave only 9-23 and 9-26 (eq.…”

Section: Introductionmentioning

confidence: 99%

Steric effects in the phototransposition reactions of dialkylbenzenes

Gonzalez¹,

Pincock²

2006

Can. J. Chem.

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The photochemistry, photophysical properties, and temperature dependence (-25 to +65°C) of fluorescence by quantum yields and excited singlet state lifetimes in acetonitrile have been examined for three sets of dialkylbenzene derivatives: Set 1 -ortho-xylene (10), tetralin (11), and indan (12); Set 2 -2,3-dimethylbenzonitrile (9-23), 5-cyanotetralin (T-23), and 4-cyanoindan (I-23); and Set 3 -3,4-dimethylbenzonitrile (9-34), 6-cyanotetralin (T-34), and 5-cyanoindan (I-34). Phototransposition reactions occur for 10, 9-23, 9-34, and T-34. Fitting of the temperature-dependent fluorescence data to an Arrhenius expression gave A and E a values for all substrates studied except I-23 and I-34. The fluorescence intensity of these two compounds was essentially independent of temperature. For the other compounds, the data revealed that the activation barrier separating the excited singlet state (S 1 ) from the reactive intermediate, a prefulvene biradical, was the important one in determining the reaction efficiency. The dominant mode of decay of the reactive intermediate was internal return to the starting material. Moreover, the general observation was made that nitrile substitution ortho to one of the alkyl groups in these dialkylbenzene derivatives reduced the rate at which they were converted to the reactive intermediate and, therefore, also the efficiency of the phototransposition reactions.Résumé : En se basant sur les rendements quantiques ainsi que les temps de vie de l'état singulet excité observés lors de réactions dans l'acétonitrile, on a étudié la photochimie, les propriétés photophysiques et la relation entre la tempé-rature (-25 à +65°C) et les rendements quantiques pour trois ensembles de dérivés benzéniques dialkylés, soit l'ensemble 1 formé d'ortho-xylène (10), de tétraline (11) et d'indane (12); l'ensemble 2 formé de 2,3-diméthylben-zonitrile (9-23), de 5-cyanotétraline (T-23) et de 4-cyanoindane (I-23); l'ensemble 3 formé de 3,4-diméthylbenzonitrile (9-34), de 6-cyanotétraline (T-34) et de 5-cyanoindane (I-34). Il se produit des réactions de phototransposition pour les composés 10, 9-23, 9-34 et T-34. Un ajustement des données de fluorescence influencées par la température à une expression d'Arrhenius permet de calculer les valeurs A et E a pour tous les substrats étudiés, à l'exception de I-23 et I-34. L'intensité de la fluorescence de ces deux composés est essentiellement indépendante de la température. Pour les autres composés, les données ont permis de déterminer que la barrière d'activation qui sépare S 1 , l'état singulet excité, de l'intermédiaire réactif, un biradical préfulvène, est celle qui est importante dans la détermination de l'efficacité de la réaction. Le mode dominant dans la désactivation de l'intermédiaire réactif est le retour interne vers le produit de dé-part. De plus, on a observé que la présence d'un substituant nitrile en position ortho par rapport aux groupes alkyles de ces dialkylbenzènes provoque une réduction de la vitesse avec laquelle ils se transforment en intermédiaire...

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Benzvalene, the Tricyclic Valence Isomer of Benzene

Cited by 155 publications

References 2 publications

Let’s Play with Valence Isomers: The Influence of Different Main Group Elements on Their Relative Stability

Let’s Play with Valence Isomers: The Influence of Different Main Group Elements on Their Relative Stability

Theoretical Investigation of Stable Structures of Ge<SUB>6</SUB> Clusters with Various Negative Charges

Steric effects in the phototransposition reactions of dialkylbenzenes

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