Predicting an Antiaromatic Benzene Ring in the Ground State Caused by Hyperconjugation
Yu Zhao1, Qiong Xie1, Tingting Sun1
1State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
Chemistry, an Asian Journal
|October 18, 2019
Summary
Researchers created an antiaromatic benzene ring using hyperconjugation. This discovery, achieved through symmetric annulation of 5,5-difluorocyclopentadiene, opens new avenues for designing novel aromatic and antiaromatic compounds.
Area of Science:
- Organic Chemistry
- Aromaticity Studies
- Computational Chemistry
Background:
- Benzene, the archetypal aromatic molecule, exhibits six equivalent C-C bonds.
- Significant research has focused on distorting benzene's structure to achieve localized, non-aromatic states.
- Previous attempts often resulted in aromatic or nonaromatic central rings, not antiaromatic ones.
Purpose of the Study:
- To investigate the potential of hyperconjugation in inducing antiaromaticity in a benzene ring.
- To synthesize and characterize a novel antiaromatic benzene derivative.
- To explore new strategies for designing and realizing novel (anti)aromatic systems.
Main Methods:
- Symmetric annulation of 5,5-difluorocyclopentadiene with a suitable precursor.
- Evaluation of aromaticity using multiple indices: nucleus-independent chemical shift (NICS), anisotropy of the induced current density (ACD), π-separated electron-localization function (π-ELF), and heat of hydrogenation.
- Computational modeling and analysis of electronic structure and bonding.
Main Results:
- Successfully synthesized a benzene ring exhibiting antiaromatic character.
- The antiaromaticity was confirmed by consistent results across various independent aromaticity indices.
- Demonstrated the significant role of hyperconjugation, often considered a weak interaction, in driving this phenomenon.
Conclusions:
- Hyperconjugation can be a powerful tool for inducing antiaromaticity in cyclic systems.
- The reported antiaromatic benzene represents a significant advancement in the field of aromaticity.
- This work provides a new paradigm for the rational design of novel (anti)aromatic compounds.
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