Question

{Which statements are True? A. In Hoffmann bromamide degradation, 4 moles of NaOH and 2 moles of \( \mathrm{Br_2} \) are consumed per mole of an amide. B. Hoffmann bromamide reaction is not given by alkyl amides. C. Primary amines can be synthesized by Hoffmann bromamide degradation. D. Secondary amide on reaction with \( \mathrm{Br_2} \) and NaOH will give secondary amine. E. The by-products of Hoffmann degradation are \( \mathrm{Na_2CO_3} \), \( \mathrm{NaBr} \) and \( \mathrm{H_2O} \). Choose the correct answer from the options given below:}

• A. A, C and E only
• B. B, C and D only
• C. C and E only
• D. C, D and E only

Hint:

Hoffmann bromamide degradation: \[ \mathrm{RCONH_2 \rightarrow RNH_2} \] Always remember:

• Only primary amides react
• One carbon atom is lost
• Product formed is always a primary amine

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The Hoffmann bromamide degradation reaction is a signature organic method used to convert a primary amide into a primary amine containing one fewer carbon atom. The pathway involves treating the primary amide with bromine ($\text{Br}_2$) in an aqueous or ethanolic solution of sodium hydroxide ($\text{NaOH}$).
Step 2: Key Formula or Approach:
The balanced chemical equation for the standard Hoffmann bromamide degradation is: \[ \text{R-CONH}_2 + \text{Br}_2 + 4\text{NaOH} \rightarrow \text{R-NH}_2 + \text{Na}_2\text{CO}_3 + 2\text{NaBr} + 2\text{H}_2\text{O} \] Let's evaluate each statement individually using this benchmark mechanism.
Step 3: Detailed Explanation:
- Statement A: According to the balanced equation, $1 \text{ mole}$ of primary amide reacts with $4 \text{ moles}$ of $\text{NaOH}$ and $1 \text{ mole}$ of $\text{Br}_2$. Statement A states that $2 \text{ moles}$ of $\text{Br}_2$ are consumed, which is incorrect. Thus, A is false. - Statement B: Both aliphatic (alkyl) amides and aromatic (aryl) amides readily undergo this degradation to form corresponding primary amines. Thus, B is false. - Statement C: The chief synthetic function of this reaction is the clean preparation of primary aliphatic or aromatic amines ($\text{R-NH}_2$). Thus, C is true. - Statement D: The reaction mechanism strictly requires a primary amide ($\text{R-CONH}_2$) because it requires two acidic protons attached to the nitrogen to undergo the initial $N$-bromination and subsequent deprotonation stages. Secondary amides ($\text{R-CONHR}'$) do not undergo this transformation. Thus, D is false. - Statement E: From the balanced reaction stoichiometry, the formed inorganic by-products are explicitly sodium carbonate ($\text{Na}_2\text{CO}_3$), sodium bromide ($\text{NaBr}$), and water ($\text{H}_2\text{O}$). Thus, E is true. Reviewing our choices, only statements C and E are true.
Step 4: Final Answer:
The correct option is (3) which includes C and E only.