Question

What is the difference between elimination and substitution reactions?

Answer 1

ELIMINATION REACTION	SUBSTITUTION REACTION
1.Substitution reaction is the type of reaction in which a functional group or Atom us replaced by another functional group or atom.	1.Elimination is the type of reaction in which atoms are removed from the molecule either in pairs or in groups.
2.This type of reaction can occur only at a very high temperature.	2.This type of reaction can occur at low or room temperature.
3.There are two types of Elimination reaction - ${\mathrm{E}}_1\mathrm{and}{\mathrm{E}}_2$.	3.There are two types of Nucleophilic Substitution reaction- ${\mathrm{S}}_{\mathrm{N}1}\mathrm{and}{\mathrm{S}}_{\mathrm{N}2}$.
4.In ${\mathrm{E}}_1$ elimination ,the rate of reaction is proportional to the rate of product formation only, thus it is an unimolecular reaction and follows first order kinetics. It is also the rate determining step.	4.In ${\mathrm{S}}_{\mathrm{N}1}$reaction, the rate of reaction depends only on the concentration of Substrate and this is a slow step and thus the rate determining step.
5.In ${\mathrm{E}}_2$ mechanism, the rate of reaction is proportional to the concentration of both the eliminating agent and substrate, thus it is a bimolecular reaction and follows second order kinetics.	5.In ${\mathrm{S}}_{\mathrm{N}2}$ reaction, the rate of reaction depends on the concentration of both the substrate as well as the nucleophile.
6.There are generally two types of elimination reaction of basis of removal of group or atoms that are Dehydration and Dehydrohalogenation.	6.The type of electrophilic substitutions on Aromatic compounds are Halogenation, Sulphonation, Friedel Crafts reactions, Nitration , Acyclation.
7.In dehydration reaction there will be a loss of Water molecule whereas in Dehydrohalogenation there will be loss of a Hydrogen and a Halogen atom.	7.
8.Example of elimination reaction-	8.Example of substitution reaction.