Question

How does a reaction ${S_N}2$ affect stereochemistry?

Answer 1

Hint In order to know how ${S_N}2$ reaction will affect the stereochemistry; we must first know what a stereochemistry is. Stereochemistry is said to be a branch of chemistry which helps us to study about the spatial arrangement of the atoms present in a molecule.

Complete step by step solution:
Let us first understand the ${S_N}2$ mechanism.
- ${S_N}2$ mechanism is said to be the bimolecular nucleophilic substitution reaction.
-The rate of ${S_N}2$ mechanism will depend on the concentration of two species namely nucleophile and substrate.
-This is a second order reaction. It is a one-step mechanism.
- In the ${S_N}2$ mechanism the nucleophile will attack the substrate from the backside of the reactant.

Now let us see about stereochemistry. Stereochemistry is said to be a branch of chemistry which helps us to study about the spatial arrangement of the atoms present in a molecule.
- The stereochemistry of the product, in the ${S_N}2$ mechanism is inverted, when compared to that of the substrate. In the ${S_N}2$ mechanism the nucleophile will attack the substrate from the side opposite to the leaving group. Therefore, it is said to attack from the backside. During this attack the stereochemistry will change. Hence it is said to have an inversion of configuration.

Note: We have to note that ${S_N}2$and ${S_N}1$ mechanisms are different from one another. Let us compare ${S_N}2$and ${S_N}1$

${S_N}2$ mechanism	${S_N}1$ mechanism
It is a One-step process	It is a Two-step process
The Rate of the reaction will depend on two species	The Rate of the reaction will depend on only one species.
It is favored by non-polar solvents.	It is favored by polar solvents.
Bimolecular.	Unimolecular.
Second order reaction.	First order reaction.