What are practical requirement for selectivity of SN2 over SN1 reaction for getting SN2 product in chemistry?
As a simplification, If the substrate is sterically very bulky, then SN1 If the substrate is much less crowded, then SN2 in a ‘medium’ case, a mixture of the two processes can occur. Another factor is stabilization of a carbocation intermediate by either induction from subtituents on the substrate, or by coordination by the solvent. Increased stibilization will increase the probablility of SN1, since SN2 does not have a carbocation intermediate. A small less bulky nucleophile will tend to favor the SN2 process.
