Organic chemistry (Amines)
An organic compound (A) with the molecular formula C8H9NO when treated with bromine in aqueous solution of sodium hydroxide gives a new compound (B) having the molecular formula C7H9N. The compound (B) on heating with chloroform and ethanolic potassium hydroxide forms a compound (C) having foul-smelling. Further, the compound (B) gives an alkali soluble sulphonamide on reacting with benzenesulfonyl chloride.
Moreover, a thermally unstable compound (D) is obtained when the compound (B) reacts with sodium nitrite in concentrated hydrochloric acid at very low temperature. Further, the compound (D) on heating with water yields a compound which gives colour with neutral ferric chloride solution.
Answer the following questions on the basis of this passage.
The name of the reaction converting compound A to B is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Hofmann Bromamide Degradation
In the Hofmann bromamide degradation, an amide gives a primary amine with one carbon atom fewer:
\( \displaystyle \ce{RCONH2 + Br2 + 4NaOH -> RNH2 + Na2CO3 + 2NaBr + 2H2O} \)
A is \( \ce{C8H9NO} \) and B is \( \ce{C7H9N} \): one carbon and one oxygen are lost, which matches this reaction. Here A is a toluamide (\( \ce{CH3C6H4CONH2} \)) and B is a toluidine (\( \ce{CH3C6H4NH2} \)). So the reaction is the Hofmann bromamide degradation.
Why the other options are incorrect
Option (1) Diazotization — Incorrect. This converts B into the diazonium salt D with \( \ce{NaNO2} \)/HCl; it is a later step.
\( \displaystyle \ce{CH3C6H4NH2 + NaNO2 + 2HCl} \xrightarrow{\text{273-278 K}} \ce{CH3C6H4N2^+Cl^- + NaCl + 2H2O} \)
Option (2) Bromination — Incorrect. Bromination would add bromine to the molecule. B contains no bromine, and a carbon atom has been lost.
Option (4) Ammonolysis — Incorrect. Ammonolysis of a haloalkane with \( \ce{NH3} \) gives amines without any loss of carbon.
\( \displaystyle \ce{RX + NH3 -> RNH2 + HX} \)
NCERT (2026-27 edition):
Hofmann Bromamide Degradation Reaction
