The correct order of the following compounds showing increasing tendency towards nucleophilic substitution reaction is :

Solution

Chemistry ma’am · 3 steps

Each ortho or para nitro group stabilises the carbanion, so more nitro groups means faster substitution.

1. Why aryl halides resist. In chlorobenzene the C–Cl bond has partial double-bond character from resonance, and the electron-rich ring repels a nucleophile. So plain chlorobenzene reacts with OH⁻ only under very harsh conditions.
2. Role of nitro groups. The nucleophile first adds to the carbon carrying Cl, giving a negatively charged intermediate (a Meisenheimer complex), and then Cl⁻ leaves. A NO₂ group at the ortho or para position pulls this negative charge onto its own oxygen atoms. That stabilises the intermediate, and each extra such group makes the reaction faster.

   Compound	Ortho/para NO₂ groups	Conditions to give the phenol
   (i) chlorobenzene	0	NaOH, 623 K, 300 atm
   (ii) 4-nitrochlorobenzene	1 (para)	NaOH, 443 K
   (iii) 2,4-dinitrochlorobenzene	2 (ortho, para)	NaOH, 368 K
   (iv) 2,4,6-trinitrochlorobenzene	3 (both ortho, para)	warm water is enough

3. So. The milder the conditions needed, the more reactive the compound: (i) < (ii) < (iii) < (iv), which is option (d).

The idea to keep. In nucleophilic substitution of haloarenes, electron-withdrawing groups at ortho and para positions help, not hinder. Count them: the more there are, the faster the reaction.

Answer from the NTA final answer key. Solution by PrepWiser.