The correct order of reactivity of following haloarenes towards nucleophilic substitution with aqueous NaOH is: Choose…

Step 1: Understand $S_NAr$ mechanism

Nucleophilic aromatic substitution requires:

1. Electron-withdrawing groups (EWG) to activate
2. EWG at ortho or para positions (resonance stabilization)
3. Strong nucleophile

Step 2: Analyze each compound

(A) Chlorobenzene:

• No activating EWG
• Very slow or no reaction
• Lowest reactivity ✗

(B) o-Nitrochlorobenzene:

• One $\ce{NO2}$ at ortho position
• Strong EWG, can stabilize Meisenheimer complex
• Moderate reactivity ✓

(C) Chlorobenzene with $\ce{NO2}$ at meta and $\ce{OMe}$ at ortho:

• $\ce{NO2}$ at meta (cannot stabilize through resonance)
• $\ce{-OMe}$ at ortho (EDG, deactivates the ring)
• Conflicting effects: EWG at wrong position + EDG
• Low reactivity ✗

(D) Chlorobenzene with two $\ce{NO2}$ groups:

• Multiple strong EWG
• If at ortho/para positions: very strong activation
• Highest reactivity ✓✓

Step 3: Order reactivity

Reactivity order:

D (2 NO₂) > B (1 NO₂ ortho) > A (no activation) > C (NO₂ meta + OMe)

Wait, the answer shows D > B > A > C, which means C is slowest.

This makes sense because:

• C has NO₂ at meta (no resonance stabilization)
• C has OMe (EDG, deactivates)
• The combination makes it even less reactive than plain chlorobenzene

Answer: (d) D > B > A > C

Key Factors:

Activating factors:

• Number of EWG (more = faster)
• Position of EWG (ortho/para > meta)
• Strength of EWG (NO₂ > CN > CHO)

Deactivating factors:

• EDG present (OMe, OH, NH₂)
• EWG at meta position (no resonance)

Reactivity order:

• 2,4-Dinitro >> ortho-Nitro ≈ para-Nitro > meta-Nitro > No activation
• EDG + meta-EWG < No activation (conflicting effects)