what is functional group

A functional group is a group of atoms or bonds inside a substance that is responsible for the substances unique chemical reactions in organic chemistry. In organic chemistry, the functional group approach is used to classify large numbers of compounds according to their reactions. A functional group is a substituent or moiety in a molecule that causes the molecules characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecules composition. This enables systematic prediction of chemical reactions and behavior of chemical compounds and the design of chemical synthesis. The reactivity of a functional group can be modified by other functional groups nearby. Functional groups are groups of one or more atoms with distinctive chemical properties regardless of what is attached to them. The atoms of functional groups are bound by covalent bonds with one another and with the rest of the molecule. Some of the most common functional groups include hydroxyl, present in alcohols and phenols; carboxyl, present in carboxylic acids; carbonyl, present in aldehydes, ketones, and quinones; and nitro, present in certain organic nitrogen compounds.