Photochemistry of ethylidenecyclooctenes. Mechanism of bicyclobutane formation

Dauben, William G.; Ritscher, James S.

doi:10.1021/ja00712a059

Cited by 56 publications

(39 citation statements)

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“…The constancy of the stereochemical pathway followed indicated that most likely the ring closure to the cyclopropane ring was a concerted process, the stereochemistry of which follows the orbital symmetry requirements for the closure of an allylic system. This finding was reminiscent of our earlier results related to the conversion of a * This material was prepared in a similar manner tothat employed for 16 10 • In this latter process, it was postulated that the reaction was initiated from the twisted, relaxed conformation of the excited state (Chart IV). It was shown that one cyclopropane ring was formed by a conrotatory ring closure; the orthogonal orbital not being part part of the three-atom basis set was free from orbital symmetry requirements and it formed a bond with the nearest orbital to complete the reaction.…”

supporting

confidence: 53%

Steric aspects of the photochemistry of conjugated dienes and trienes

Dauben¹,

Kellogg²,

Seeman³

et al. 1973

Pure and Applied Chemistry

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The photochemical transformation of the 1 ,3-cyclohexadiene chromophore can Iead via orbital symmetry allowed pathways either to a bicyclo[2.2.0]hex-2-ene derivative or to a 1 ,3,5-hexatriene derivative. It was established that the ground state conformation of the starting 1 ,3-cyclohexadiene controls the primary photochemical reaction. The photoproducts composition can be changed by variation of the wavelength or of the temperature. The mechanisms of these processes are discussed. The photochemical transformation of a 1 ,3,5-hexatriene derivative to a bicyclo[3.1.0]hex-2-ene has been shown to proceed from an s-trans,s-cis conformation. The mechanism of the rearrangement has been shown tobe an extension ofthe rearrangement ofa 1,3-butadiene to a bicyclo[l.l.O]butane.In the study ofthe photochemistry of 1 ,3-cyclohexadienes, the evaluation ofthe photoequilibrium between the diene and the resultant triene is important

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supporting

confidence: 53%

Steric aspects of the photochemistry of conjugated dienes and trienes

Dauben¹,

Kellogg²,

Seeman³

et al. 1973

Pure and Applied Chemistry

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“…Owing to the unequal Coulombic integrals, the degeneracy between the so-If the usual PPP approach is used (i.e., ai = 0 and lutions of the [2,4] and [4,2] CI blocks is removed. Therefore, it is possible to understand the appearance of the "sudden polarization" as well as the polarity of the particular ionic states as is illustrated subsequently.…”

Section: B J J = Andaj;t + Aand?jjmentioning

confidence: 99%

“…The scheme which illustrates the configuration interaction among the configurations with a single electron transfer belonging to the CI block [2,4] is given in Figure 2. The configurations with two or more electron transfers have considerably higher energies and, therefore, are omitted from the scheme.…”

Section: B J J = Andaj;t + Aand?jjmentioning

confidence: 99%

Nature of the “sudden polarization” effect and its role in photochemistry

Koutecký

Bonačić‐Koutecký

Čı́žek

et al. 2009

Int. J. Quantum Chem.

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The "sudden polarization" effect is described within the framework of the four-state model of asymmetrical diradicals. Its applicability for photochemical predictions is illustrated by the results obtained from the ob initio minimal-basis-set calculations followed by a very limited CI. The analysis of the reasons for the large charge separation in the low-lying singlet excited states and their particular polarities has been performed with the PPP full C1 approach. The connection between an alternant-symmetry braking within the r-electron model and the origin of the "sudden polarization" effect for the hydrocarbon intermediates is demonstrated. A possible extension of similar phenomena to the excited states of molecular system with pronounced polar character is discussed.

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“…Such an electron distribution is exhibited by the significant structure I/3. The large and similar weights for I/3 and II/3 indicate that the allyl anion [50] and allyl cation [51] structures are both relevant for the 1 1 B u p,p* state. Structures I/3 and II/3 (Scheme 2) contain one covalent and one ionic p bond.…”

Section: Resultsmentioning

confidence: 88%

“…The relevance of these two resonance structures for the characterization of the 1 1 B u p,p* state has been debated in the past. Dauben and Ritscher [50] inferred from the photoreactivity of ethylidene cyclooctenes that an allyl-anion ± methyl-cation electronic arrangement is relevant for the reactivity of the diene system. This conclusion is in agreement with the importance of structure II/3.…”

Section: Resultsmentioning

confidence: 99%

The Photochemistry of 1,3-Butadiene Rationalized by Means of Theoretical Resonance Structures and Their Weights

Bachler

Schaffner

2000

Chem. Eur. J.

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A complete active-space self-consistent-field wave function for the pi-electron part of s-trans-1,3-butadiene has been expanded into a set of localized bonding schemes and their weights. These bonding schemes are close to the resonance structures used in organic chemistry. The expansion technique has been applied to both the electronic ground state and the electronically first-excited singlet and triplet pi,pi* states. The manifolds of large-weight bonding schemes represent approximate resonance hybrids for the ground and the singlet and triplet pi,pi* states of s-trans-1,3-butadiene. These resonance hybrids, obtained by theory alone, permit a qualitative rationalization of a significant part of the known singlet and triplet photochemistry.

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Photochemistry of ethylidenecyclooctenes. Mechanism of bicyclobutane formation

Cited by 56 publications

References 0 publications

Steric aspects of the photochemistry of conjugated dienes and trienes

Steric aspects of the photochemistry of conjugated dienes and trienes

Nature of the “sudden polarization” effect and its role in photochemistry

The Photochemistry of 1,3-Butadiene Rationalized by Means of Theoretical Resonance Structures and Their Weights

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