The SN1 reaction is a nucleophilic substitution reaction with a unimolecular rate-determining step. It's an organic substitution reaction. SN1 is an abbreviation for substitution nucleophilic unimolecular. A carbocation intermediate is formed in this reaction. It is commonly observed in tertiary or secondary alkyl halide reactions with secondary or tertiary alcohols under extremely acidic or very basic circumstances. In inorganic chemistry, the SN1 reaction is known as the dissociative mechanism.
SN2 Reaction
It is a coordinated one-step reaction mechanism in which carbon-halogen bond breaking and carbon-nucleophile bond creation occur simultaneously. It is bimolecular and operates on a second-order kinetic basis. The reaction rate is determined by the concentrations of the substrate (alkyl halide) and the nucleophile. The reaction center possesses inversion stereochemistry.
SN1 will be faster if :
The reagent is a weak base
The solvent is polar protic (Eg- water and alcohols which lack acidic proton and are polar)
Carbon in the leaving group is tertiary (connected to three carbon atoms)
SN2 will be faster if :
The reagent is a strong base
Carbon in the leaving group is connected to the primary or a methyl group
the solvent that is used is polar protic
Thus, both these reactions depend upon these factors. For example, the SN1 reaction will be faster if the reagent is a weak base.
