Elimination Reactions

Elimination reactions are reverse of the addition reactions. 2 or 4 atoms or groups attached to the adjacent carbon atoms to a substrate molecule are eliminated to form a multiple bond.

These reactions are like nucleophilic substitution may also divided into two classes

E1 Reactions (Elimination unimolecular) :

At the rate of an elimination reaction is dependant only upon the concentration of substrate and in dependent of concentration of the nucleophile. the reaction is of first order and is designed as E1 like SN reaction are also two step process first step involves slow ionization of the alkyl halides to the carbonium ions and second step involves fast abstraction of a proton by the base by the adjacent beta carbon atom leading to the formation of alkenes.

Step1 :

Step2 :

E2 Reaction (Elimination Bimolecular)

At the rate of elimination reaction is dependant both upon the concentration of a substrate and nucleophile the reaction is of second order represented as E2 like SN2 is also a one step process in which Abstraction of a proton from the alpha carbon atom occurs simultaneously.