Given below are two statement: one is labelled as
Assertion (A) and the other is labelled as Reason (R):
Assertion (A): undergoes S_N2 reaction faster than .

Reason (R): Iodine is a better leaving group because of its large size.

In the light of the above statements, choose the correct answer from the options given below: 

CONCEPT:

SN2 Reaction and Leaving Group

• SN2 (Substitution Nucleophilic Bimolecular) reaction is a single-step reaction where the nucleophile attacks the substrate and the leaving group departs simultaneously.
• The rate of SN2 reaction depends on factors such as steric hindrance, the strength of the nucleophile, and the nature of the leaving group.
• A good leaving group facilitates the reaction. A good leaving group is one that can stabilize the negative charge after leaving the substrate.
• In halides, the leaving group ability increases with size due to better stabilization of the negative charge. Thus, Iodine (I^-) is a better leaving group than Bromine (Br^-).

EXPLANATION:

• Assertion (A): "undergoes SN₂ reaction faster than ." This statement is true because iodine is a better leaving group compared to bromine due to its larger size and ability to stabilize the negative charge more effectively.
• Reason (R): "Iodine is a better leaving group because of its large size." This statement is true and correctly explains the assertion.

In SN₂ reactions, the leaving group plays a crucial role in determining the reaction rate. Since iodine is a better leaving group than bromine, the substrate with iodine will undergo the SN₂ reaction faster.

Therefore, the correct answer is Both A and R are true and R is the correct explanation of A.