In the following sequence of reactions: The end product(C) is :

The correct answer is Option (4) → Ethyl alcohol

The sequence adds one carbon through the cyanide ion, turns the nitrile into a carboxylic acid and then reduces the acid to a primary alcohol.

• A = CH₃CN (ethanenitrile): the cyanide ion replaces bromide by nucleophilic substitution.

      \( \ce{CH3Br + KCN -> CH3CN + KBr} \)

• B = CH₃COOH (ethanoic acid): the nitrile is hydrolysed to the amide and then to the acid.

      \( \ce{CH3CN} \xrightarrow{\ce{H3O+}} \ce{CH3CONH2} \xrightarrow{\ce{H3O+}} \ce{CH3COOH + NH4+} \)

• C = CH₃CH₂OH (ethyl alcohol): \( \ce{LiAlH4} \) reduces the carboxylic acid to the primary alcohol.

      \( \ce{CH3COOH} \xrightarrow[\text{(ii) }\ce{H2O}]{\text{(i) }\ce{LiAlH4}/\text{ether}} \ce{CH3CH2OH} \)

Why the other options are incorrect

• Option (1) Acetone — Incorrect. A ketone is not formed; \( \ce{LiAlH4} \) reduces acids to alcohols.

• Option (2) Methane — Incorrect. No decarboxylation takes place in this sequence.

• Option (3) Acetaldehyde — Incorrect. \( \ce{LiAlH4} \) does not stop at the aldehyde stage; it reduces the acid fully to the alcohol.

NCERT (2026-27 edition):
From Nitriles and Amides – “Nitriles are hydrolysed to amides and then to acids in the presence of H⁺ or OH^– as catalyst. Mild reaction conditions are used to stop the reaction at the amide stage.”

Reactions Involving –COOH Group – “… Carboxylic acids are reduced to primary alcohols by lithium aluminium hydride or better with diborane.”

Note: The same/similar question has been asked in different years by NTA as per the details given below: