Nomenclature

The naming of arenes depends upon the the number of substituents on the ring.

Mono-substituted Arenes

The name of the substituent is named first followed by the parent name "benzene".

If it has an alkyl substituent that is longer than 6 carbons it is named as a phenyl substituted alkane instead.  For example;

Disubstituted Benzenes

With disubstituted benzenes we use the ortho (o), meta(m) and para(p) descriptors.  Relative to the carbon that the Z group is attached (the ipso carbon), there are three other possible positions ortho, meta and para around the ring.

 

For example;

If you recognize a common named arene then you can use it as the parent name.

Poly-substituted Benzenes

If the benzene ring has more than two substituents you must use a numbering system.  You want to use the lowest possible set of numbers.  In the following example we have a 2,4,1 versus 3,1,4.  Since 2+4+1=7 is less than 3+1+4=8 the first way is correct.

If you get the same set off numbers then go with alphabetical precedence.  for example we could begin counting on the bromine or chlorine atoms.  Since B comes before C in the alphabet you should start numbering on the bromine.

If you recognize a common named benzene structure you can use it as the parent name. You begin counting at the ipso carbon of the common named substituent.