Elimination Reaction Versus Substitution Reaction...!

 

Elimination versus substitution :

Alkyl halides undergo substitution as well as elimination reaction. Both reactions are brought about by basic reagent, hence there is always a competition between these two reactions. The reaction which actually predominates depends upon following factors.

(a) Nature of alkyl halides: Tertiary alkyl halides prefer to undergo elimination reaction whereas primary alkyl halides prefer to undergo substitution reaction.

(b) Strength and size of nucleophile: Bulkier electron rich species prefers to act as base by abstracting proton, thus favours elimination. Substitution is favoured in the case of comparatively weaker bases, which prefer to act as nucleophile.

(c) Reaction conditions: Less polar solvent, high temperarture favours elimination whereas low temperature, polar solvent favours substitution reaction.