Given below are two statement: one is labelled asAssertion (A) and the other is labelled as Reason(R):Assertion (A): undergoes SN2 reactionfaster than .Reason (R): Iodine is a better leaving groupbecause of its large size.In the light of the above statements, choose thecorrect answer from the options given below:

Answer

SN2 Reaction and the Role of Leaving Groups

The rate of an SN2 reaction depends significantly on the tendency of the leaving group to depart.

• 1-Iodobutane reacts faster than 1-chlorobutane in SN2 reactions.

Reason: Superior Leaving Group Ability of Iodide

• Iodide ion (I⁻) is a larger, more polarizable anion compared to chloride (Cl⁻).
• Its size and polarizability allow it to disperse negative charge more effectively, making it a more stable ion in solution.
• As a result, iodide is a significantly superior leaving group than chloride.

Conclusion

In SN2 mechanisms, the stability and charge distribution of the leaving group are critical. Since iodide ion disperses charge better, it enhances reaction rate, making 1-iodobutane more reactive than 1-chlorobutane.