Question

From the following which pairs give the faster SN2 reaction?

• A.
• B.
• C.
• D.

Hint:

In SN2 reactions, the rate of reaction is directly influenced by the leaving group. The better the leaving group (I > Br > Cl), the faster the reaction.

Answer 1

The Correct Option is A

In SN2 reactions, the reaction rate depends on the ability of the leaving group to leave.
The halide ions (Cl\(^-\), Br\(^-\), and I\(^-\)) are good leaving groups, but the rate of the reaction increases with the size of the leaving group.
Iodide (I\(^-\)) is a better leaving group than bromide (Br\(^-\)), and bromide is better than chloride (Cl\(^-\)). Therefore, for the fastest SN2 reaction, the best pairs are the ones where the leaving group is iodide (I) or bromide (Br).
Thus, the correct answer is (a).