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Chemistry · Glossary

What is Aromaticity?

Also known as: aromatic · antiaromatic

Definition 16.11 University Chemistry — Year 2 · Chapter 16 — Hückel Theory and Conjugated Systems

A cyclic, planar, fully conjugated system is aromatic when its π\pi electrons form a closed shell with a large delocalisation energy, and antiaromatic when its π\pi electrons half-fill a degenerate pair, which makes it less stable than the corresponding open chain.

Enthalpies of hydrogenation to cyclohexane in the gas phase, from tabulated enthalpies of formation (bars, height = heat released). Two conjugated double bonds release 10\, kJ/ mol less than twice one; benzene releases 150\, kJ/ mol less than three times one: its aromatic stabilisation.
Enthalpies of hydrogenation to cyclohexane in the gas phase, from tabulated enthalpies of formation (bars, height = heat released). Two conjugated double bonds release 10 kJ/mol10\,\mathrm{kJ}/\mathrm{mol} less than twice one; benzene releases 150 kJ/mol150\,\mathrm{kJ}/\mathrm{mol} less than three times one: its aromatic stabilisation.
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