`H_(3)C-overset(O)overset(||)(C)-NH_(2)overset(PCl_(5))(to)Aunderset(H_(2)O)overset(LiAiH_(4))(to)B`
Final product B is

Options

A. A primary alcohol
B. A primary amine
C. A secondary amine
D. a carboxylic acid

Answer

To solve the problem step by step, we will analyze the reactions taking place and identify the final product B.

### Step 1: Identify the starting compound
The starting compound is an amide, specifically:
\[ H_3C-C(=O)-NH_2 \]

### Step 2: Reaction with PCl5
When the amide reacts with phosphorus pentachloride (PCl5), it undergoes a transformation. PCl5 acts as a reducing agent and converts the amide into a nitrile (cyanide). The reaction can be summarized as follows:
\[ H_3C-C(=O)-NH_2 + PCl_5 \rightarrow H_3C-C \equiv N + POCl_3 + 2 HCl \]

### Step 3: Identify compound A
The product formed from the reaction with PCl5 is a nitrile:
\[ A: H_3C-C \equiv N \]

### Step 4: Reaction with LiAlH4
Next, the nitrile (compound A) reacts with lithium aluminium hydride (LiAlH4). LiAlH4 is a strong reducing agent that reduces nitriles to primary amines. The reaction proceeds as follows:
1. The nucleophilic hydride ion (H-) from LiAlH4 attacks the electrophilic carbon in the nitrile.
2. This leads to the formation of an intermediate that contains a carbon-nitrogen double bond (imine).
3. The addition of water (H2O) will protonate the nitrogen, converting the imine into a primary amine.

The reaction can be summarized as:
\[ H_3C-C \equiv N + 2 \text{LiAlH}_4 + H_2O \rightarrow H_3C-CH_2-NH_2 + LiCl + Al(OH)Cl \]

### Step 5: Identify compound B
The final product B formed from the reaction is:
\[ B: H_3C-CH_2-NH_2 \]
This structure represents a primary amine.

### Final Answer
The final product B is a primary amine, specifically:
\[ \text{B: Ethylamine (C}_2\text{H}_5\text{NH}_2\text{)} \]

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