Nucleophilic Substitution Reaction

Nucleophilic Substitution Reaction

Nucleophilic substitution reaction is an organic reactions where one nucleophile replaces another nucleophile. The group which takes electron pair and displaced from the carbon is known as leaving group and the molecule on which substitution takes place is known as substrate. The leaving group leaves as a neutral molecule or anion. Nucleophilic substitution reaction is of three types-
1. Unimolecular Nucleophilic Substitution Reaction (SN₁)
2. Bimolecular Nucleophilic Substitution Reaction (SN₂)
3. Internal Nucleophilic Substitution Reaction (SN_i)

Internal Nucleophilic Substitution Reaction (SN_i)

In internal nucleophilic substitution reaction, an internal nucleophilic attack from same side of leaving group occur with retention of configuration. This reaction follows 2nd order kinetics that means the rate of the reaction dependent on the concentration of both the alcohol and the thionyl chloride.

Mechanism of Internal Nucleophilic Substitution Reaction (SN_i)

SN1 Reactions	SN2 Reactions
Unimolecular reaction	Bimolecular reaction
Follows a 1st order kinetic	Follows a 2nd order kinetic
Involves in at least two steps	Involves in single step
Rate of reaction depends on the concentration of the substrate	Rate of reaction depends on the concentration of both the substrate and the nucleophile
The rate-determining step involves a single molecule	The rate-determining steps involve two molecules.
It involves rearrangements of carbocations	No rearrangements of the carbocation.
Compared to the reactant, product have both inverted and retained configuration.	Compared to the reactant, products will have an inverted configuration.
Reactivity order: 3o > 2o > 1o > methyl	Reactivity order: 3o < 2o < 1o < methyl