Role of delocalization in benzene
- Univ. of California, Berkeley, CA (United States) Lawrence Berkeley Lab., CA (United States)
- Univ. of Wisconsin, Madison, WI (United States)
The influence of [pi] delocalization on the geometry of benzene is examined at the ab initio SCF level of theory. We find that benzene favors a bond alternating geometry when its canonical [pi] MOs are replaced by three localized ethylenic orbitals, revealing that delocalization is in part responsible for the equilibrium symmetric structure. In apparent contrast, a [sigma]-[pi] energy partitioning analysis suggests that the benzene [sigma] framework is responsible for the symmetric structure, the [pi] system preferring a distorted geometry. Shaik et al. have therefore concluded that delocalization in not an important symmetrizing force in this molecule. We show, however, that the [pi] energy component contains a sizable and strongly geometry dependent contribution from the localized (Kekule) wave function. Thus, it appears to be misleading to judge the nature of delocalization based on a [sigma]-[pi] partition. We conclude that delocalization effects act to strongly stabilize symmetric benzene in essential accord with the concepts of classical resonance theory. 27 refs., 6 figs., 2 tabs.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 7301863
- Journal Information:
- Journal of the American Chemical Society; (United States), Vol. 115:23; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
BENZENE
CHEMICAL BONDS
CONFIGURATION
ELECTRONIC STRUCTURE
MATHEMATICAL MODELS
MOLECULAR ORBITAL METHOD
THEORETICAL DATA
AROMATICS
CALCULATION METHODS
DATA
HYDROCARBONS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
400201* - Chemical & Physicochemical Properties
990200 - Mathematics & Computers