Aromaticity is a property associated with the extra stability of certain types of p systems.  Fundamentally it arises from having the maximum number of electrons in the p bonding  molecular orbitals. As we will see, it is not restricted to benzene, substituted benzenes, 6-membered rings or just hydrocarbons.

The property of aromaticity is generally about a significant extra stability associated with a resonance delocalized structure.  This extra stability moderates the reactivity of these systems compared to alkenes and means aromatics can be considered as their own functional group.
The presence of aromatic systems can also influence the reactivity of functional groups directly attached to the aromatic system particularly in the benzylic position. Therefore it is important that you are able to recognise the aromatic systems.

 

Although the name ‘aromatic’ was originated from the characteristic odor or ‘aroma’ of benzene-like compounds, chemists now have a completely different method of deciding whether a compound is aromatic or not. Based on the analysis of a number of compounds with unusual resonance stabilization energies, the following characteristics have been accepted as criteria for aromaticity.