Photosolvation of benzene. Mechanism of formation of bicyclo[3.1.0]hex-3-en-2-yl and of bicyclo[3.1.0]hex-2-en-6-yl derivatives

Kaplan, Louis; Rausch, David J.; Wilzbach, K. E.

doi:10.1021/ja00779a089

Cited by 43 publications

(18 citation statements)

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“…However, the ε value, which is directly related to the calculated value of k f by eq. [6], also seems anomalously high. Although we have rechecked the ε value several times for this compound, including with a repurified sample, and both NMR spectra and GC analysis indicated no impurities, we suspect that this value is incorrect.…”

Section: Photophysical Properties Of the Compounds Of Sets 1-3mentioning

confidence: 92%

“…[6], the general theoretical relationship between the radiative lifetime (τ f = 1/k f ) and the absorbance spectrum, n is the refractive index of the solvent, υ f is the expectation value for the frequency of the fluorescence spectrum, and the final term is the integrated molar absorptivity over the S 0 to S 1 transition in the absorbance spectrum. The constant gives k f in units of s -1 if the frequency values are expressed in wavenumber (cm -1 ) and molar absorptivity ε in the usual units ((mol/L) -1 cm -1 ).…”

Section: Photophysical Properties Of the Compounds Of Sets 1-3mentioning

confidence: 99%

“…The integrated spectra needed to obtain k f values from eq. [6] were obtained by summing the 1 nm incremental areas (the absorbance values converted to ε by dividing by the molar concentration) over the complete absorption band. These areas are somewhat uncertain at the short wavelength end because of the overlap with the long wavelength tail of the S 2 band so that the absorbance does not reach zero.…”

Section: -Cyanoindan (I-34)mentioning

confidence: 99%

“…The expectation values necessary for calculating the k f values from eq. [6] were obtained by summing the 1 nm incremental areas over the complete emission band. For temperaturedependent quantum yield measurements, a 1 cm cuvette was thermostatted with stirring in a cuvette holder equipped with a Quantum Northwest TLC 50 temperature controller, which allows relative fluorescence measurements at 5°C intervals from -25 to 65°C in acetonitrile over a 3 h time span.…”

Section: -Cyanoindan (I-34)mentioning

confidence: 99%

“…[3]) for benzene-d 6 in 2,2,2-trifluoroethanol (TFE) on photolysis in alcohol solvents (5,6). Research in this area up until 1980 has been the subject of several reviews (7)(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Photophysical Properties Of the Compounds Of Sets 1-3mentioning

confidence: 92%

Section: Photophysical Properties Of the Compounds Of Sets 1-3mentioning

confidence: 99%

Section: -Cyanoindan (I-34)mentioning

confidence: 99%

Section: -Cyanoindan (I-34)mentioning

confidence: 99%

“…[3]) for benzene-d 6 in 2,2,2-trifluoroethanol (TFE) on photolysis in alcohol solvents (5,6). Research in this area up until 1980 has been the subject of several reviews (7)(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

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Steric effects in the phototransposition reactions of dialkylbenzenes

Gonzalez¹,

Pincock²

2006

Can. J. Chem.

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Spirokonjugation

Schweig¹,

Weidner²,

Hellwinkel³

et al. 1973

Angew. Chem.

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In zwei zueinander senkrechten und durch ein tetraedrisches Atom verknupften a-Systemen konnen diejenigen MOs beider Systeme durch Spirokonjugation[21 miteinander in Wechselwirkung treten, deren endstandige 2p,-AOs (Zp,-AOs an den dem tetraedrischen Atom benachbarten Atomen) jeweils antisymmetrisch zueinander sindI31. Diese endstiindigen antisymmetrischen 2p,-AOs in den beiden Teilsystcmen konnen relativ zueinander zwei Anordnungen einnehmen: ( A ) spiroantibindend und ( B ) spirobindend. Die Differenz zwischen den Energien der spiroantibindenden ( A ) und spirobindenden (B) Kombinationen wird ,,Spiroaufspaltung" genannt. Das Konzept der Spirokonjugation wurde urspriinglich an Spiroverbindungen entwickelt. In vorangegangenen Ar-beitenlJl haben wir in den strukturell &lichen Nicht-Spiroverbindungen Tetravinylmethan (CH2=CH)& ( 5 ) und Tetravinylsilan (CH,=CH)$i (6) erstmals Spirokonjugation photoelektronenspektroskopisch nachgewiesen. Bei diesen Verbindungen haben wir Annahmen zur Molekiilgeometrie (D2,-Symmetrie) zugrundelegen mussen, da diese nicht wie bei Spiroverbindungen durch Ringbildung fixiert ist. AulJerdem treten Zuordnungsprobleme auf, da der Energieabstand zwischen dem nicht zur Spirokonjugation berihigten HOMO (,,highest occupied M O ) und dem unmittelbar darunterliegenden, an der Spirokonjugation beteiligten MO in den n-Systemen von Dimethyldivinylmethan Me,C(CH=CH,), und Dimethyldivinylsilan Me,Si(CH=CH,), kleiner ist als die auftretenden Aufspaltungen (Jahn-Teller-Aufspaltung der HOMOs und Spiroaufspaltung der darunterliegenden MOs). Diese Probleme konnen durch Untersuchung von Spiroverbindungen geeigneter Struktur (die HOMOs der beiden Ringe sind zur Spirokonjugation befahigt und liegen Si / \ M e M e [*I Prof. Dr. A. Schweig und Dip].-Chem. U. Weidner Fachbereich Physikalische Chemie der IJniversitiit 355 Marburg, BiegenstraBe 12 Prof. Dr. D. Hellwinkel und DipLChem. W. Krapp lnvtitul fur Organische Chemie der Universitait 69 Heidelberg. Im Neuenhcimer Feld 7genugend hoch iiber den anderen rr-MOs) ausgeschaltet werden. Der so mogliche direkte und eindeutige Beweis der Spirokonjugation ist uns jetzt anhand der Photoelektronen(PE)-Spektren von 9,9-Dimethylfluoren ( I ) , 9,9-Dimethyl-9-silafluoren (2), 9,9'-Spirobifluoren (3) und 9,9-Spirobi(9-silafluoren) (4) gelungen. Abbildung 1 zeigt die PE-Spektren von ( 1 ) bis ( 4 ) . DieSpektren von ( I ) und (2) zeigen die gleiche Signalstruktur (Intensitaten von @ : @ : @ = 1 : 2 : 1) wie Biphenyl ( 7)lsl. Daraus geht hervor, daR die obersten besetzten MOs in ( I ) und (2) nahe verwandt mit den entsprechenden MOs in (7) sind und daD damit insbesondere das HOMO in 7 8 9 1 0 7 8 9 IP[eVI-Abb. 1. Photoelektronenspektren [9] von 9.9-Dimethylfluoren ( I ), 9.9-Dimethyl-9-silafluoren ( 2 ), 9.9'-Spirobifluoren ( 3 ) und 9,9'-Spirobi(9-silafluoren) ( 4 ) . Die venikalen Ionisierungspotentiale (in eV) und relativenIntensitaten sind: f i r ( I ): @ 7.8/1. @ 8.75/1.8, @ 9.75/1.0; fur (2): @ 7.9/1, @ 8.8011.5, @ 9.7 und @ 10.25/2.7; fur ( 3 ) : @ 7.7!1. @ 8.011.3, ...

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