Question
Explain isomerism in arenes.
Solution
Arenes show position isomerism in their molecules. The isomers differ with respect to the relative positions of the alkyl substituents. In disubstituted derivates (-CH3 group on the substituent), three isomers are possible.
Similarly, three position isomers of trimethyl benzene are:
In the case of bicyclic arenes such as naphthalene, even monosubstituted compounds show position isomerism. For example. 
