Question:
Which of the following compounds is most reactive in SN$_1$ reaction?
Which of the following compounds is most reactive in SN$_1$ reaction?
Show Hint
SN\(_1\) rate \( \propto \) carbocation stability:
\[ \text{Benzylic/Allylic} > 3^\circ > 2^\circ \gg 1^\circ > \text{Vinylic} \]
Resonance stabilization dominates.
\[ \text{Benzylic/Allylic} > 3^\circ > 2^\circ \gg 1^\circ > \text{Vinylic} \]
Resonance stabilization dominates.
Updated On: Mar 2, 2026
- Option a
- Option b
- Option c
- Option d
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Concept:
SN\(_1\) reactivity depends on carbocation stability:
Resonance stabilization increases stability
Allylic and benzylic carbocations are highly stable
Vinylic carbocations are unstable
Step 1: Compare options
(B) Forms highly resonance-stabilized allylic carbocation
(A) Less resonance delocalization
(C) Only secondary carbocation
(D) Vinylic carbocation unstable
Conclusion:
Most stabilized carbocation \( \Rightarrow \) fastest SN\(_1\).
SN\(_1\) reactivity depends on carbocation stability:
Resonance stabilization increases stability
Allylic and benzylic carbocations are highly stable
Vinylic carbocations are unstable
Step 1: Compare options
(B) Forms highly resonance-stabilized allylic carbocation
(A) Less resonance delocalization
(C) Only secondary carbocation
(D) Vinylic carbocation unstable
Conclusion:
Most stabilized carbocation \( \Rightarrow \) fastest SN\(_1\).
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