Question

Propionamide on Hofmann degradation gives-
A. Methyl amine
B. Ethyl amine
C. Propyl amine
D. Ethyl cyanide

Answer 1

Hint: Propionamide is an amide compound with general formula \[RCON{H_2}\] . The compound formed has one less carbon atom than the amide.

Complete Step by Step Solution:
Hoffmann degradation reaction is a type of reaction where primary amide is converted to a primary amine. The reaction takes place in presence of a strong base which attacks the amide. The reaction takes place by heating the primary amide using a halogen mixture of chlorine or bromine, a strong base and water.

In this reaction, halogen mainly reacts with sodium hydroxide which forms sodium hypobromite which changes the primary amide into an isocyanate intermediate. Water attacks the isocyanate intermediate causing the proton transfer and resulting in the formation of ammonium cation. Due to the thermal condition, the carbon dioxide explodes and after quenching ammonium cation, a primary amine product is formed.

When propionamide is heated with bromine in presence of potassium hydroxide or when propionamide undergoes Hofmann degradation, the product formed is ethyl amine.
The Hoffman degradation reaction of propionamide is shown below.

Image: Hofmann degradation reaction of propionamide
Therefore, the correct option is B.

Note: Hofmann degradation reaction is also termed as Hoffmann bromamide reaction. There is another term known as Hofmann elimination reaction in which tertiary amines and alkenes are formed as a product by reacting quaternary ammonium with methyl iodide and heating the compound formed with silver oxide and water.
The general reaction is shown below.

Image: Hofmann elimination reaction