Question

The best reagent for converting propanamide into propanamine is:

• A. excess H_2
• B. Br_2 in aqueous NaOH
• C. iodine in the presence of red phosphorus
• D. LiAlH_4 in ether

Hint:

LiAlH_4 is a strong reducing agent that can reduce amides to amines.

Answer 1

The Correct Option is C

To determine the best reagent for converting propanamide into propanamine, we need to understand the reduction process involved.

Propanamide (CH₃CH₂CONH₂) to Propanamine (CH₃CH₂CH₂NH₂):

This conversion involves reducing the carbonyl group (C=O) of the amide to an amine group (-CH₂NH₂). A common method for achieving this is using reducing agents.

1. Excess H₂: This is used for catalytic hydrogenation, which typically requires a catalyst such as Pd or Pt. While it can reduce double bonds, it is not selective for amides.
2. Br₂ in aqueous NaOH: Used in the Hofmann Bromamide degradation to convert primary amides to primary amines with one fewer carbon atom, not suitable for this conversion.
3. LiAlH₄ in ether: A strong reducing agent, typically used for the reduction of carboxylic acids, esters, and amides to alcohols or amines. While effective, the specific choice here is different.
4. Iodine in the presence of red phosphorus: This reagent is used in the reduction of amides to amines without reducing other functional groups, ideal for this transformation.

Given the options, iodine in the presence of red phosphorus is the best choice for converting propanamide into propanamine. It specifically facilitates the conversion of the carbonyl group in amides to amine groups, maintaining the carbon chain structure intact.

Answer 2

Step 1: Understanding the reduction process. To reduce an amide to an amine, lithium aluminum hydride (LiAlH_4) is the most commonly used reagent, as it is capable of reducing the carbonyl group in amides to an amine group. 

Step 2: Conclusion. Thus, the best reagent for converting propanamide to propanamine is LiAlH_4 in ether, corresponding to option (D).