Details
| Original language | English |
|---|---|
| Pages (from-to) | 5949-5953 |
| Number of pages | 5 |
| Journal | Journal of the American Chemical Society |
| Volume | 116 |
| Issue number | 13 |
| Publication status | Published - 1 Jun 1994 |
| Externally published | Yes |
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.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Catalysis
- Chemistry(all)
- General Chemistry
- Biochemistry, Genetics and Molecular Biology(all)
- Biochemistry
- Chemical Engineering(all)
- Colloid and Surface Chemistry
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In: Journal of the American Chemical Society, Vol. 116, No. 13, 01.06.1994, p. 5949-5953.
Research output: Contribution to journal › Article › Research › 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 -