What is a functional group? Give examples of four different functional groups.

An atom or group of atoms in an organic compound that defines the structure of a family of compounds and determines the properties of the family is called the functional group.

A functional group is responsible for the characteristic property or behavior of a class of compounds. For example, hydroxyl ( –OH) group in alcohols.

Examples of functional groups are: Hydroxyl group ( –OH), Aldehyde group ( –CHO), Ketone group ( –CO) and carboxylic group ( –COOH).