91Ó°ÊÓ

The reaction in which two or more reactant molecules react to form a single product molecule is called an addition reaction.

For example, A+B$→$AB

Elimination is a type of chemical reaction in which two substituents are removed from a molecule to give a product is called elimination reaction.

For example, when cyclohexanol is heated with sulphuric acid then the product of the reaction is cyclohexene.

The reaction in which one functional group in a chemical compound is replaced by another functional group is called a substitution reaction.

For example, when methane is react with chlorine in the presence of high radiation then it gives chloromethane and.

A reaction in which an ion, atom, or any chemical unit migrates within the same chemical compound is called a rearrangement reaction.

For example, claisen rearrangement

(a)${\mathrm{CH}}_3\mathrm{Br}+\mathrm{KOH}→{\mathrm{CH}}_3\mathrm{OH}+\mathrm{KBr}$

The reaction is a substitution reaction.

(b)${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}→{\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+\mathrm{HBr}$

The above reaction is an elimination reaction.

(c)${\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+{\mathrm{H}}_2→{\mathrm{CH}}_3{\mathrm{CH}}_3$

The above reaction is an addition reaction.