In the given reaction, the end-product is-
\( \ce{CH3COOH} \xrightarrow[\Delta]{\ce{NH3}} \mathrm{A} \xrightarrow{\ce{NaOBr}} \mathrm{B} \xrightarrow[\ce{H2O}]{\ce{NaNO2/HCl}} \mathrm{C} \)
C is-
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Methyl alcohol
The sequence converts an acid to an amide, then to an amine with one carbon fewer, and finally to an alcohol:
First, acetic acid is heated with ammonia. The ammonium salt formed loses water and gives acetamide, A:
\( \displaystyle \ce{CH3COOH + NH3 -> CH3COONH4} \xrightarrow{\Delta} \ce{CH3CONH2 + H2O} \)
Then acetamide undergoes the Hoffmann bromamide degradation with NaOBr (\( \ce{Br2} \) + NaOH): the methyl group migrates to nitrogen and CO is lost as carbonate, giving methylamine, B, with one carbon fewer:
\( \displaystyle \ce{CH3CONH2 + Br2 + 4NaOH -> CH3NH2 + Na2CO3 + 2NaBr + 2H2O} \)
Finally, the primary aliphatic amine reacts with nitrous acid (\( \ce{NaNO2} \) + HCl). The unstable aliphatic diazonium salt breaks down, releasing \( \ce{N2} \) and giving methanol, C:
\( \displaystyle \ce{CH3NH2 + HNO2} \xrightarrow{\ce{NaNO2 + HCl}} \ce{CH3OH + N2 ^ + H2O} \)
Why the other options are incorrect
Option (1) Ethyl alcohol — Incorrect. This would need an amine with two carbons; the Hoffmann step removes one carbon, leaving only one.
Option (3) Acetaldehyde — Incorrect. No step here forms a carbonyl compound; nitrous acid converts the primary amine into an alcohol.
Option (4) Methylamine — Incorrect. This is B, the intermediate; it reacts further with nitrous acid.
NCERT (2026-27 edition):
Hoffmann Bromamide Degradation Reaction – “Hoffmann developed a method for preparation of primary amines by treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide. In this degradation reaction, migration of an alkyl or aryl group takes place from carbonyl carbon of the amide to the nitrogen atom. The amine so formed contains one carbon less than that present in the amide.”
Reaction with Nitrous Acid – “… (a) Primary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively and alcohols. Quantitative evolution of nitrogen is used in estimation of amino acids and proteins.”