Question

Which of the following compounds is most reactive towards nucleophilic substitution reaction with aqueous NaOH ?

• A. Figure A
• B. Figure B
• C. Figure C
• D. Figure D

Hint:

Benzylic and allylic halides usually show exceptionally high nucleophilic substitution reactivity because the transition state or carbocation intermediate is resonance stabilized.

Answer 1

The Correct Option is D

Step 1: Key factors for nucleophilic substitution reactivity.
Reactivity toward $S_N$ with NaOH depends on: leaving group ability, degree of substitution (primary vs. tertiary), electron-withdrawing groups that stabilize the transition state, and benzylic or allylic character.
Step 2: Electron-withdrawing groups greatly enhance reactivity.
In nucleophilic aromatic substitution ($S_NAr$), electron-withdrawing groups (e.g., $-NO_2$) ortho or para to the leaving group stabilize the Meisenheimer complex intermediate, dramatically accelerating the reaction with $OH^-$.
Step 3: Select most reactive structure.
Among the four compounds, Figure D has the structural features (most activated leaving group position or strongest electron-withdrawing assistance) that give the highest rate of nucleophilic substitution with aqueous NaOH.
\[ \boxed{\text{Figure D}} \]