Which of the following classes of compounds on hydrolysis yields carboxylic acids?
(A) \( RCN \)
(B) \( RCONH_2 \)
(C) \( RCOCl \)
(D) \( RCOOR \)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (B), (C) and (D)
Nitriles, amides, acid chlorides and esters are all derivatives of carboxylic acids: each contains the carbon of the –COOH group bonded to another group (N, \( \ce{NH2} \), Cl or OR′). Hydrolysis replaces that group by –OH and gives back the carboxylic acid (as the free acid in acidic solution, or as its salt in alkaline solution, which is then acidified).
(A) RCN — Correct. A nitrile is hydrolysed, through the amide, to the acid by dilute acid or alkali: \( \ce{R-C#N + 2H2O + H^+ -> R-COOH + NH4^+} \).
(B) \( \ce{RCONH2} \) — Correct. An amide is hydrolysed on heating with acid or alkali: \( \ce{R-CONH2 + H2O + H^+ -> R-COOH + NH4^+} \).
(C) RCOCl — Correct. An acid chloride is hydrolysed readily, even by cold water: \( \ce{R-COCl + H2O -> R-COOH + HCl} \).
(D) RCOOR — Correct. An ester is hydrolysed by acid (reversibly) or by alkali (saponification, giving the salt): \( \ce{R-COOR' + H2O <=> R-COOH + R'OH} \).