Question

Which of the following reagents are used to prepare primary amines by Hofmann bromamide degradation reaction?

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

Hint:

{Hofmann Rearrangement Shortcut:} Amide \( \rightarrow \) Amine with {one carbon less}. Reagents to remember: \[ Br_2 + NaOH \quad (\text{basic bromine}) \]

Answer 1

The Correct Option is C

Concept: The
Hofmann bromamide degradation reaction (also called Hofmann rearrangement) is used to convert a primary amide into a primary amine with
one carbon less. The reaction involves rearrangement and loss of the carbonyl carbon as \( CO_2 \). General reaction: \[ R{-}CONH_2 \xrightarrow{Br_2/NaOH} R{-}NH_2 + CO_2 \] Thus, the essential reagents are:

• Primary amide (\( R{-}CONH_2 \))
• Bromine (\( Br_2 \))
• Strong base (NaOH or KOH)

Step 1: Analyze each given option.
(i) \( R{-}CONH_2 \): This is the starting compound (primary amide). \(\Rightarrow\) Required.
(ii) NaOH: Provides the basic medium needed for rearrangement and formation of hypobromite intermediate. \(\Rightarrow\) Required.
(iii) \( Br_2 \): Essential reagent that forms sodium hypobromite (\( NaOBr \)) in situ. \(\Rightarrow\) Required.
(iv) CHCl\(_3\): Used in the carbylamine reaction (test for primary amines), not in Hofmann rearrangement. \(\Rightarrow\) Not required.
Step 2: Final selection. Correct set of reagents: \[ (i), (ii), (iii) \] \[ \therefore \text{Correct answer = (C)} \]