Question

Match List-I with List-II

Choose the correct answer from the options given below :

• A. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
• B. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
• C. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
• D. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)

Hint:

The reactivity of aryl halides towards nucleophilic substitution increases significantly with the presence of electron-withdrawing groups (especially nitro groups) at ortho and para positions. The more the number of such groups, the milder the conditions required for the substitution reaction.

Answer 1

The Correct Option is C

Step 1: Analyze the conversions in List-I and the reagents/conditions in List-II.
The conversions involve the replacement of a chlorine atom on an aromatic ring by a hydroxyl group, forming a phenol. This is a nucleophilic aromatic substitution reaction. The reactivity of aryl halides towards nucleophilic substitution is greatly influenced by the presence of electron-withdrawing groups (like nitro groups) at ortho and para positions to the chlorine atom. More nitro groups activate the ring towards nucleophilic attack, allowing the reaction to proceed under milder conditions.
Step 2: Match each conversion with the appropriate reagents and conditions.
(A) \( C_6H_5Cl \rightarrow C_6H_5OH \) (Chlorobenzene to Phenol): Chlorobenzene has no activating groups. The nucleophilic substitution of chlorine by \( OH^- \) requires harsh conditions (high temperature and high pressure) to overcome the stability of the C-Cl bond and the electron-rich aromatic ring. The Dow process uses NaOH at around 623 K and 300 atm, followed by acidification to yield phenol. Thus, (A) matches with (IV). (B) \( p-ClC_6H_4NO_2 \rightarrow p-HOC_6H_4NO_2 \) (p-Nitrochlorobenzene to p-Nitrophenol): The presence of one nitro group at the para position activates the chlorine towards nucleophilic substitution. The reaction can be carried out under milder conditions compared to chlorobenzene. NaOH at 368 K followed by acidification is sufficient for this conversion. Thus, (B) matches with (II). (C) \( 2,4-Cl(NO_2)_2C_6H_3 \rightarrow 2,4-OH(NO_2)_2C_6H_3 \) (2,4-Dinitrochlorobenzene to 2,4-Dinitrophenol): The presence of two nitro groups at ortho and para positions strongly activates the chlorine towards nucleophilic substitution. The reaction proceeds readily with warm aqueous NaOH followed by acidification. Thus, (C) matches with (I). (D) \( 2,4,6-Cl(NO_2)_3C_6H_2 \rightarrow 2,4,6-OH(NO_2)_3C_6H_2 \) (2,4,6-Trinitrochlorobenzene to 2,4,6-Trinitrophenol (Picric Acid)): The presence of three nitro groups at ortho and para positions makes the chlorine atom extremely susceptible to nucleophilic attack. Even mild conditions like warm water can cause the hydrolysis of the C-Cl bond to form picric acid. Thus, (D) matches with (III).
Step 3: Write down the matching pairs.
(A) - (IV)
(B) - (II)
(C) - (I)
\ (D) - (III)
Step 4: Choose the option that corresponds to the correct matching.
The correct matching is (A)-(IV), (B)-(II), (C)-(I), (D)-(III), which corresponds to option (3).