aromatic ring

An aromatic hydrocarbon (abbreviated as AH) or arene is a hydrocarbon, the molecular structure of which incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent. This sweet scent actually came from impurities in the compounds (which are not actually aromatic in the sense initially described). The configuration of six carbon atoms in aromatic compounds is known as a benzene ring, after the simplest possible aromatic hydrocarbon, benzene. Aromatic hydrocarbons can be monocyclic or polycyclic.
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(Ar) An exceptionally stable planar ring of atoms with resonance structures that consist of alternating double and single bonds, e. g. benzene: