Question

explain functional isomerism with example

Answer 1

The concept of functional isomerism is pretty easy. Functional isomerism is also known as structural isomerism and the basic mechanism of functional isomerism is there are few compounds having same molecular numbers. When such type of compounds combines together to form a long chain, then despite of different homologous series they show functional isomerism. 
Eg: Propanal shows functional isomerism.

Answer 2

Functional Isomerism is a phenomenon in which compounds have same chemical formula but different functional group.

Explanation :

• When a compound have same molecular formula but functional groups are different they are called functional isomers and phenomenon is called Functional isomerism.
• They are also called Functional group isomers. They are the type of a structural isomerism. There are many examples of functional isomerism which are propanal and popanone and ethanol and dimethyl ether.
• For example - Ethanol ($C_2H_5OH$) and dimethyl ether ($CH_3OCH_3$). Number of carbons, oxygens and hydrogens are same in both cases but functional groups are different, one is alcohol and other is ether.