Related Experiment Videos
The acenes: is there a relationship between aromatic stabilization and reactivity?
P von Ragué Schleyer1, M Manoharan, H Jiao
1Computational Chemistry Annex, Department of Chemistry, University of Georgia, Athens, Georgia 30602-2525, USA. schleyer@chem.uga.edu
Organic Letters
|November 9, 2001
Summary
Acene reactivity increases with size, but their aromaticity per electron remains constant. Inner rings are more reactive and aromatic than outer rings, challenging traditional understanding of acene stability.
Area of Science:
- Organic chemistry
- Computational chemistry
- Physical chemistry
Background:
- Acenes, polycyclic aromatic hydrocarbons, exhibit increasing reactivity with size.
- Understanding the relationship between reactivity and aromaticity in acenes is crucial for predicting their chemical behavior.
Purpose of the Study:
- To investigate the correlation between reactivity and aromaticity in acenes.
- To determine the factors influencing the reactivity of individual acene rings.
- To compare the aromaticity of different acene rings and benzene.
Main Methods:
- Computational calculation of reaction energies and activation energies for acene reactions.
- Analysis of nucleus-independent chemical shifts (NICS) to quantify aromaticity.
- Correlation analysis between reactivity, reaction energies, and product stabilities.
Main Results:
- Acene resonance energies per pi electron remain nearly constant despite increasing overall reactivity from benzene to heptacene.
- Computed activation energies for individual acene rings correlate with reaction energies and depend on product stabilities.
- Nucleus-independent chemical shifts reveal that more reactive inner acene rings are more aromatic than less reactive outer rings and even benzene.
Conclusions:
- Acene reactivity is governed by a complex interplay of reaction energies, product stabilities, and localized aromaticity.
- Inner acene rings possess higher aromaticity and reactivity compared to outer rings, suggesting a deviation from simple linear extrapolation of properties.
- The findings challenge conventional notions of acene aromaticity and reactivity trends.