This article is about a chemical property of molecules. For meanings related to
odor, see
aroma compound. Aromaticity is a chemical property in which a
conjugated ring of
unsaturated bonds,
lone pairs, or
empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. It can also be considered a manifestation of cyclic
delocalization and of
resonance.This is usually considered to be because
electrons are free to cycle around circular arrangements of
atoms, which are alternately single- and double-
bonded to one another. These bonds may be seen as a hybrid of a single bond and a double bond, each bond in the ring identical to every other. This commonly-seen model of aromatic rings, namely the idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds (cyclohexatriene), was developed by
Kekulé (see "History" section below). The model for
benzene consists of two
resonance forms, which corresponds to the double and single bonds' switching positions. Benzene is a more stable molecule than would be expected without accounting for charge delocalization.
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A type of hydrocarbon, such as benzene or toluene, with a specific type of ring structure. Aromatics are sometimes added to gasoline in order to increase octane. Some aromatics are toxic.
PIANTE AROMATICHE. SOSTANZE AROMATICHE. COMPOSTI AROMATICI
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