Organic reactions are broadly divided into the following four categories :
I) Substitution Reactions : When an atom or group of atoms from a molecule is replaced by another atom or group of atoms, it is known as a substitution reaction.
ii) Addition Reactions : When an atom or group of atoms are added to a substrate molecule, which is unsaturated, it is known as addition reaction. In this reaction there is a net gain of atoms in the product molecule
iii) Elimination Reactions : When atoms or group of atoms are removed from a molecule resulting in the formation of multiple linkage in that molecule, it is known as elimination reaction. The loss of atoms or group of atoms may occur from the same atom or different atoms in the molecule.
iv) Rearrangement Reactions : When atoms or group of atoms within the molecule simply change their position to give the product, it is known as a rearrangement reaction. It may appear as an internal substitution reaction has occured.
