Isomerism is a special feature of catenated organic compounds.
For example, if we consider the molecular formula of an organic compound to be C2H6O, we will not be able to name the compound. This is because the molecular formula of an organic compound represents only the number of different atoms present in that compound. It does not indicate the way in which the atoms are arranged and hence its structure.
The phenomenon in which the same molecular formula may exhibit different structural arrangements is called isomerism.
The given formula C2H6O can be represented with two kinds of arrangements.
Both the compounds have same molecular but different kind of arrangement. In compound ‘a’ the oxygen atom is attached to a hydrogen and a carbon. It is an alcohol. Whereas, compound ‘b’ the oxygen atom is attached to two carbon atoms and it is an ether. Both these compounds have different physical and chemical properties.