Question

Increasing order of the nucleophilic substitution of following compounds is

• A. I $<$ III $<$ II $<$ IV
• B. II $<$ I $<$ III $<$ IV
• C. II $<$ III $<$ I $<$ IV
• D. IV $<$ III $<$ I $<$ II

Hint:

SNAr reactivity increases with:
Strong \(-M\) groups (NO\(_2\), CN)
Multiple EWGs increase rate dramatically
EDGs reduce substitution

Answer 1

The Correct Option is B

Concept: Nucleophilic aromatic substitution (SNAr) is enhanced by:

• Electron-withdrawing groups (NO$_2$)
• Ortho/para activation

Electron-donating groups decrease reactivity. Step 1: Identify substituent effects

• II: OCH$_3$ (EDG) \(\Rightarrow\) least reactive
• I: No activating group
• III: One NO$_2$ (EWG) \(\Rightarrow\) increased reactivity
• IV: Two NO$_2$ groups \(\Rightarrow\) highest activation

Conclusion: \[ \text{II} < \text{I} < \text{III} < \text{IV} \]