Any of a large class of organic compounds whose molecular
structure includes one or more planar rings of atoms, usually but not always
six carbon atoms.
The ring's carbon-carbon bonds (see bonding) are neither
single nor double but a type characteristic of these compounds, in which
electrons are shared equally with all the atoms around the ring in an electron
cloud. The term was first applied c. 1860 to a class of hydrocarbons isolated
from coal tar and distinguished by odours much stronger than those of other
classes of hydrocarbons. In modern chemistry, aromaticity denotes the chemical
behaviour, especially the low reactivity, of this class of molecules related to
their bonding. The parent compound of this class is benzene (C6H6). See also
hydrogenation.
Source:Britannica encyclopedia
