What is Sn Mechanism of reactions?
Nucleophilic substitution is the reaction of an electron pair donor (the nucleophile, Nu) with an electron pair acceptor (the electrophile). An sp3-hybridized electrophile must have a leaving group (X) in order for the reaction to take place.
Mechanism of Nucleophilic Substitution
The term SN2 means that two molecules are involved in the actual transition state:
The departure of the leaving group occurs simultaneously with the backside attack by the nucleophile. The SN2 reaction thus leads to a predictable configuration of the stereocenter - it proceeds with inversion (reversal of the configuration).
In the SN1 reaction, a planar carbenium ion is formed first, which then reacts further with the nucleophile. Since the nucleophile is free to attack from either side, this reaction is associated with racemization.