# Isomerism in Organic Compounds

The phenomenon of existence of two or more compounds possessing the same molecular formula but different properties is known as isomerism.

# Structural Isomerism

Compounds having the same molecular formula but different structures (manners of linking the atoms) are classified as structural isomers. Some typical examples of different types of structural isomerism are given below.
1. Chain isomerism: When two or more compounds have similar molecular formula but different carbon skeletons, these are referred to as chain isomers and the phenomenon is termed as chain isomerism. For example, C5H12 represents three compounds

1. Position isomerism: When two or more compounds differ in the position of substitutent atom or group on the carbon skeleton, they are called position isomers and this phenomenon is termed as position isomerism. For example, the molecular formula C3H8O represents two alcohols:

1. Functional isomerism
Two or more compounds having the same molecular formula but different functional groups are called functional isomers and this phenomenon is termed functional isomerism. For example, the molecular formula C3H6O represents an aldehyde and a ketone:

and C3H8O represents ether and an alcohol.

C2H5OCH3            H3C CH2 CH2OH
Ethyl methyl ether         Propanol

1. Metamerism
It arises due to unequal distribution of alkyl groups on either side of the functional group in the molecule. For example, C4H10O represents methoxypropane(CH3OC3H7) and ethoxyethane(C2H5OC2H5).