IUPAC Nomenclature of Aromatic Compounds

The most important members of aromatic compounds are benzene and its derivatives. For naming an alkyl substituted benzene, the carbon atoms of benzene are numbered from 1 to 6 by giving the lowest possible number to the position of the side chain or substituent.

Benzene forms only one mono-substituted derivatives like methylbenzene or ethylbenzene.

Benzene can form three di-substituted compounds namely 1,2; 1,3 and 1,4 derivatives. These are also known as ortho- (or o–), meta- (or m-) and para- (or p-) substituted compounds, respectively.