Question

Which of the following reagents are used to prepare primary amines by Hoffmann bromamide degradation reaction ? \[ (i)\quad \begin{array}{c} O\\ || \end{array} R-C-NH_2 \] \[ (ii)\quad NaOH \] \[ (iii)\quad Br_2 \] \[ (iv)\quad CHCl_3 \]

• A. (i), (ii) and (iv)
• B. (i) and (iii)
• C. (i), (ii) and (iii)
• D. (i), (iii) and (iv)

Hint:

Hoffmann bromamide degradation converts an amide into a primary amine containing one carbon atom less. Always remember the reagents: \[ RCONH_2 + Br_2 + NaOH \] Amide + Bromine + Sodium hydroxide.

Answer 1

The Correct Option is C

Step 1: Write the overall Hoffmann bromamide reaction.
\[ RCONH_2 + Br_2 + 4NaOH \rightarrow RNH_2 + Na_2CO_3 + 2NaBr + 2H_2O \] From the balanced equation, the three reagents consumed are the amide $(i)$, $Br_2$ $(iii)$, and $NaOH$ $(ii)$.
Step 2: Confirm the role of each reagent.
The amide provides the starting material. $Br_2$ brominates the amide nitrogen. $NaOH$ (alkaline medium) facilitates the rearrangement and expels the carbonyl carbon as $CO_3^{2-}$, giving a primary amine with one carbon fewer.
Step 3: Eliminate $CHCl_3$.
Chloroform $(iv)$ is used in the Carbylamine reaction to make isocyanides from primary amines, not in Hoffmann degradation. It plays no role here and must be excluded. The correct set is $(i)$, $(ii)$, and $(iii)$.
\[ \boxed{(i),\;(ii),\;(iii)} \]