Question

What is the loss in molar mass when a primary amine is obtained by Hofmann degradation of amide?

• A. $32\text{ g mol}^{-1}$
• B. $14\text{ g mol}^{-1}$
• C. $28\text{ g mol}^{-1}$
• D. $30\text{ g mol}^{-1}$

Hint:

Hofmann degradation "degrades" the chain by one carbon atom ($C=O$).

Answer 1

The Correct Option is C

Step 1: Concept Hofmann bromamide degradation converts an amide ($R-CONH_2$) to a primary amine ($R-NH_2$) with one fewer carbon atom.

Step 2: Meaning The carbon atom of the carbonyl group ($C=O$) is lost as a carbonate ($CO_3^{2-}$) ion.

Step 3: Analysis The group lost is effectively a Carbonyl group ($CO$). Molar mass of $CO = 12 (C) + 16 (O) = 28 \text{ g/mol}$.

Step 4: Conclusion The loss in molar mass from amide to amine is $28 \text{ g/mol}$. Final Answer: (C)