Question

Haloarenes cannot undergo nucleophilic substitution by $S_N1$ mechanism.

• A. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Assertion is incorrect but Reason is correct.

Answer 1

Answer: (A)

Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.

Answer 2

Haloarenes resist $S_N1$ due to the high instability of the phenyl carbocation intermediate formed in the rate-determining step. The $sp^2$ hybridized phenyl cation is energetically unfavorable compared to alkyl carbocations. Thus, the self-ionisation leading to this unstable cation does not readily occur, preventing the $S_N1$ mechanism.