Propanamide ` underset( KOH ) overset( Br _2 ) to A overset( (i) HNO_2 ) underset((ii) Red P,HI) to B ,` here [B ] is :

Options

A. N-ethyl acetamide
B. Propane
C. Ethane
D. Acetone

Answer

To solve the given question step by step, we will go through the reactions involving propanamide and identify the products formed at each stage.

### Step 1: Identify the structure of Propanamide
Propanamide has the structure:
\[ \text{CH}_3\text{CH}_2\text{C(=O)NH}_2 \]
This can be simplified as:
- Ethyl group (C2H5) attached to a carbonyl (C=O) and an amine (NH2).

### Step 2: Reaction with Br2 and KOH
When propanamide is treated with bromine (Br2) in the presence of potassium hydroxide (KOH), it undergoes the Hofmann bromamide degradation reaction.

1. **Deprotonation**: The KOH deprotonates the amine group, forming a negatively charged nitrogen:
\[ \text{CH}_3\text{CH}_2\text{C(=O)NH}_2 \xrightarrow{\text{KOH}} \text{CH}_3\text{CH}_2\text{C(=O)NH}^- \]

2. **Bromination**: The negatively charged nitrogen attacks one of the bromine atoms, leading to the formation of a bromamide:
\[ \text{CH}_3\text{CH}_2\text{C(=O)NHBr} \]

3. **Deprotonation**: The hydroxide ion (OH-) again deprotonates the nitrogen, leading to:
\[ \text{CH}_3\text{CH}_2\text{C(=O)N}^- \text{Br} \]

4. **Migration**: The ethyl group migrates to the nitrogen, resulting in the formation of ethyl cyanate:
\[ \text{CH}_3\text{CH}_2\text{N} \equiv \text{C} \text{(C=O)} \]

### Step 3: Hydrolysis of Ethyl Cyanate
When ethyl cyanate is treated with water, it hydrolyzes to form ethanol:
\[ \text{CH}_3\text{CH}_2\text{OH} \]
This is product A.

### Step 4: Reaction with HNO2
When ethanol (A) is treated with nitrous acid (HNO2), it forms an intermediate diazonium salt:
\[ \text{CH}_3\text{CH}_2\text{N}_2^+ \]
This intermediate decomposes, releasing nitrogen gas (N2) and forming ethanol:
\[ \text{CH}_3\text{CH}_2\text{OH} \]

### Step 5: Reduction with Red Phosphorus and HI
When ethanol is treated with red phosphorus (P) and hydroiodic acid (HI), it undergoes reduction to form ethane:
\[ \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Red P, HI}} \text{C}_2\text{H}_6 \]

### Conclusion
Thus, the final product B is ethane (C2H6).

### Final Answer
**B is Ethane (C2H6)**.

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