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

Concept: Hoffmann bromamide degradation (also called Hoffmann rearrangement) converts a primary amide into a primary amine containing one carbon less than the parent amide. General reaction: \[ \mathrm{RCONH_2 + Br_2 + 4NaOH \rightarrow RNH_2 + Na_2CO_3 + 2NaBr + 2H_2O} \] Important points:

• Only primary amides undergo Hoffmann bromamide degradation.
• Product formed is a primary amine.
• One carbon atom is lost during the reaction.

Step 1: Checking Statement A. From the balanced Hoffmann bromamide degradation reaction: \[ \mathrm{RCONH_2 + Br_2 + 4NaOH \rightarrow RNH_2 + Na_2CO_3 + 2NaBr + 2H_2O} \] We observe:

• 1 mole of \( \mathrm{Br_2} \) is consumed
• 4 moles of NaOH are consumed

But Statement A says: \[ 2 \text{ moles of } \mathrm{Br_2} \] which is incorrect. Hence, Statement A is false.

Step 2: Checking Statement B. Hoffmann bromamide degradation is shown by: \[ \mathrm{RCONH_2} \] where \(R\) can be:

• Alkyl group
• Aryl group

Thus, alkyl amides definitely undergo Hoffmann degradation. Example: \[ \mathrm{CH_3CONH_2 \rightarrow CH_3NH_2} \] Therefore, Statement B is false.

Step 3: Checking Statement C. Primary amides on Hoffmann degradation produce primary amines. Example: \[ \mathrm{C_6H_5CONH_2 \rightarrow C_6H_5NH_2} \] Thus, primary amines can indeed be synthesized by this method. Hence, Statement C is true.

Step 4: Checking Statement D. Secondary amides do not undergo Hoffmann bromamide degradation because the reaction mechanism requires the presence of: \[ \mathrm{-CONH_2} \] group. Secondary amides contain: \[ \mathrm{-CONHR} \] Therefore, secondary amides do not form secondary amines in this reaction. Hence, Statement D is false.

Step 5: Checking Statement E. The balanced reaction clearly shows by-products: \[ \mathrm{Na_2CO_3,\ NaBr,\ H_2O} \] Hence, Statement E is true. Thus, only statements C and E are true. \[ \boxed{(3)\ \text{C and E only}} \]