Disubstituted benzenes, systematic naming

The term aromatic is used for historical reasons to refer to the class of compounds related structurally to benzene. Aromatic compounds are systematically named according to TUPAC rules, but many common names are also used. Disubstituted benzenes are named as ortho (1,2 disubstituted), meta (1,3 disub-stituted), or para (1,4 disubstituted) derivatives. The C6H5- unit itself is referred to as a phenyl group, and the Cb f5CH2— unit is a benzyl group. 

Because the phenol structure involves a benzene ring, the terms ortho (1,2-disubstitut-ed), meta (1,3-disubstituted), and para (1,4-disubstituted) are often used in the common names. The following examples illustrate the systematic names and the common... 

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