Theoretical studies of [n]paracyclophanes and their valence isomers

Bockisch, F.; Rayez, Jean-Claude; Dreeskamp, H.; Liotard, D.; Duguay, B.

doi:10.1007/bf01374578

Cited by 8 publications

(3 citation statements)

References 51 publications

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“…The p orbitals cannot point to the carbon atoms of the bridge and must to some degree be perpendicular to the plane of the atoms connected to the carbon that is bent out of plane. This will lead to an easier transition to the Dewar benzene when decreasing the bridge length as shown by w x various authors 14,15,17,33 . A commonly used criterion for judging aromaticity of distorted molecules is the strain energy for the molecule.…”

Section: Resultsmentioning

confidence: 89%

Aromaticity of bent benzene rings: A VBSCF study

Dijkstra¹,

Lenthe²

1999

Int. J. Quant. Chem.

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ABSTRACT:The effect of ring deformation on aromaticity has been studied for bent benzene molecules in which two carbon atoms have been bent out of plane, resulting in Ž . a boat conformation. Valence-bond self-consistent field VBSCF calculations have been performed on these molecules to obtain insight into the aromaticity of bent benzenes. Results for total energy, structure energies, weights, and orbital overlaps show that the molecule keeps its aromatic nature up to 55Њ. After 55Њ a transition to Dewar benzene occurs. The valence-bond model, by showing the weights of both Dewar and Kekulé structures, is an excellent tool to study deformed benzene.

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Section: Resultsmentioning

confidence: 89%

Aromaticity of bent benzene rings: A VBSCF study

Dijkstra¹,

Lenthe²

1999

Int. J. Quant. Chem.

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“…The bond length between the carbon atoms at positions 1 and 4 in Dewar benzene is 1.6 # A, while the distance between the 1 and 4 carbons in benzene is 2.8 # A. 15,16 When the 1-4 bond of Dewar benzene is broken to form benzene, the distance between the carbon atoms changes by 1.2 # A. Here, the displacement of atomic distance that is of interest to our examination of the state crossing is supposed to be one tenth of 1.2 # A, that is, Ák ¼ 1:2=10 Â 10 À8 cm ¼ 1:2 Â 10 À11 m. To the best of our knowledge, there are no reports of studies of the energy gap of the Dewar benzene/ benzene transformation over such intervals, i.e.…”

Section: Veri¯cation Of the Criteria: A Case Of Reaction From Dewar Bmentioning

confidence: 96%

“…The conversion of Dewar benzene to benzene, which is accompanied by chemiluminescence, has aroused the interest of many researchers; many papers dealing with this reaction have been published so far. 15,[23][24][25][26][27][28][29][30][31][32][33][34][35] Furthermore, many attempts have been made to explain the reaction, utilizing a conventional approach, by potential energy surface analysis or via conventional static correlation diagram method, applying the noncrossing rule. [28][29][30][31][32][33][34][35] The framework of Dewar benzene contains cyclobutene.…”

Section: Previous Studies On the Correlation Diagramsmentioning

confidence: 99%

Revisiting the von Neumann–Wigner noncrossing rule and validity of a dynamic correlation diagram method

Nohira

2019

J. Theor. Comput. Chem.

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The noncrossing rule for potential energy surfaces can be applied only, as originally postulated by von Neumann and Wigner, to slowly occurring changes; it has, however, over many years, been widely used to rationalize fast chemical reactions. Taking the conversion of Dewar benzene to benzene as an example, we demonstrate a reaction that has a timescale for which crossings are allowed. Since it is now established that elementary chemical reactions proceed over ca. 10–100[Formula: see text]fs, as revealed experimentally by Zewail, the noncrossing rule cannot any longer be said to be valid for most chemical reactions. We further demonstrate that the mechanism of the chemiluminescent conversion of Dewar benzene to benzene is explained by an electronic state diagram derived using a dynamic correlation diagram method which allows crossings, whereas the reaction is not explained by a conventional approach, applying the noncrossing rule using a static correlation diagram method.

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Aromaticity of bent benzene rings: A VBSCF study

Dijkstra

Lenthe

1999

Int. J. Quant. Chem.

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The effect of ring deformation on aromaticity has been studied for bent benzene molecules in which two carbon atoms have been bent out of plane, resulting in a boat conformation. Valence‐bond self‐consistent field (VBSCF) calculations have been performed on these molecules to obtain insight into the aromaticity of bent benzenes. Results for total energy, structure energies, weights, and orbital overlaps show that the molecule keeps its aromatic nature up to 55°. After 55° a transition to Dewar benzene occurs. The valence‐bond model, by showing the weights of both Dewar and Kekulé structures, is an excellent tool to study deformed benzene. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 213–221, 1999

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Theoretical studies of [n]paracyclophanes and their valence isomers

Cited by 8 publications

References 51 publications

Aromaticity of bent benzene rings: A VBSCF study

Aromaticity of bent benzene rings: A VBSCF study

Revisiting the von Neumann–Wigner noncrossing rule and validity of a dynamic correlation diagram method

Aromaticity of bent benzene rings: A VBSCF study

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