Details
Originalsprache | Englisch |
---|---|
Seiten (von - bis) | 5949-5953 |
Seitenumfang | 5 |
Fachzeitschrift | Journal of the American Chemical Society |
Jahrgang | 116 |
Ausgabenummer | 13 |
Publikationsstatus | Veröffentlicht - 1 Juni 1994 |
Extern publiziert | Ja |
Abstract
The energy differences (ΔE) between the benzene and the corresponding Dewar benzene forms of seven substituted benzenes and three [6]paracyclophanes were calculated by ab initio methods with basis sets ranging from split valence type to triple-ζ plus polarization type. Correlation effects were taken into account using second-order M⊘ller-Plesset perturbation theory (MP2). The results show that among all the investigated molecules the isomerization energy is largest for benzene itself; that is, benzene is 79 kcal/mol more stable than its Dewar form. Both, electron-accepting substituents and electron-donating substituents lower ΔE. Steric repulsion between substituents in the ortho position additionally destabilizes the benzene form relative to the Dewar form. [6]Paracyclophanes are influenced by substitution effects in the same way as the unbridged compounds. This finding can be interpreted as a further criterion for the aromaticity of the strongly deformed benzene ring in [6]paracyclophanes. Due to the deformation of the benzene ring, the ΔE values for the investigated [6]paracyclophanes are found to be considerably lower than those of the corresponding benzenes (about 25 kcal/mol). Our results are found to agree with the experimental isomerization enthalpies of hexamethylbenzene and perfluorohexamethylbenzene to within 5 kcal/mol, while a large discrepancy between theory and experiment is obtained for 8,9-dicarbethoxy[6]paracyclophane.
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- Chemie (insg.)
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- Biochemie, Genetik und Molekularbiologie (insg.)
- Biochemie
- Chemische Verfahrenstechnik (insg.)
- Kolloid- und Oberflächenchemie
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in: Journal of the American Chemical Society, Jahrgang 116, Nr. 13, 01.06.1994, S. 5949-5953.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Ab Initio Study of the Isomerization of Substituted Benzenes and [6]Paracyclophanes to the Dewar Benzene Isomers
AU - Frank, Irmgard
AU - Grimme, S.
AU - Peyerimhoff, S. D.
PY - 1994/6/1
Y1 - 1994/6/1
N2 - The energy differences (ΔE) between the benzene and the corresponding Dewar benzene forms of seven substituted benzenes and three [6]paracyclophanes were calculated by ab initio methods with basis sets ranging from split valence type to triple-ζ plus polarization type. Correlation effects were taken into account using second-order M⊘ller-Plesset perturbation theory (MP2). The results show that among all the investigated molecules the isomerization energy is largest for benzene itself; that is, benzene is 79 kcal/mol more stable than its Dewar form. Both, electron-accepting substituents and electron-donating substituents lower ΔE. Steric repulsion between substituents in the ortho position additionally destabilizes the benzene form relative to the Dewar form. [6]Paracyclophanes are influenced by substitution effects in the same way as the unbridged compounds. This finding can be interpreted as a further criterion for the aromaticity of the strongly deformed benzene ring in [6]paracyclophanes. Due to the deformation of the benzene ring, the ΔE values for the investigated [6]paracyclophanes are found to be considerably lower than those of the corresponding benzenes (about 25 kcal/mol). Our results are found to agree with the experimental isomerization enthalpies of hexamethylbenzene and perfluorohexamethylbenzene to within 5 kcal/mol, while a large discrepancy between theory and experiment is obtained for 8,9-dicarbethoxy[6]paracyclophane.
AB - The energy differences (ΔE) between the benzene and the corresponding Dewar benzene forms of seven substituted benzenes and three [6]paracyclophanes were calculated by ab initio methods with basis sets ranging from split valence type to triple-ζ plus polarization type. Correlation effects were taken into account using second-order M⊘ller-Plesset perturbation theory (MP2). The results show that among all the investigated molecules the isomerization energy is largest for benzene itself; that is, benzene is 79 kcal/mol more stable than its Dewar form. Both, electron-accepting substituents and electron-donating substituents lower ΔE. Steric repulsion between substituents in the ortho position additionally destabilizes the benzene form relative to the Dewar form. [6]Paracyclophanes are influenced by substitution effects in the same way as the unbridged compounds. This finding can be interpreted as a further criterion for the aromaticity of the strongly deformed benzene ring in [6]paracyclophanes. Due to the deformation of the benzene ring, the ΔE values for the investigated [6]paracyclophanes are found to be considerably lower than those of the corresponding benzenes (about 25 kcal/mol). Our results are found to agree with the experimental isomerization enthalpies of hexamethylbenzene and perfluorohexamethylbenzene to within 5 kcal/mol, while a large discrepancy between theory and experiment is obtained for 8,9-dicarbethoxy[6]paracyclophane.
UR - http://www.scopus.com/inward/record.url?scp=0039237514&partnerID=8YFLogxK
U2 - 10.1021/ja00092a051
DO - 10.1021/ja00092a051
M3 - Article
AN - SCOPUS:0039237514
VL - 116
SP - 5949
EP - 5953
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 13
ER -