Identify the final product (z) in the following sequence of reactions
`C_(6)H_(5)COOHunderset((ii)PBr_(3))overset((i)LiAlH_(4))rarrXoverset(KCN)rarrYoverset(LiAlH_(4))rarrZ`

Options

A. `C_(6)H_(5)CH_(2)NH_(2)`
B. `C_(6)H_(5)CH_(2)CH_(2)NH_(2)`
C. `C_(6)H_(5)CH_(2)CH_(2)CH_(2)NH_(2)`
D. `C_(6)H_(5)underset(CH_(3))underset("| ")"CH"-NH_(2)`

Answer

To identify the final product (Z) in the given sequence of reactions, we will analyze each step systematically.

### Step-by-Step Solution:

1. **Starting Material**: The reaction begins with benzoic acid, which has the formula \( C_6H_5COOH \).

2. **First Reaction with LiAlH4**:
- Benzoic acid reacts with lithium aluminium hydride (\( LiAlH_4 \)), a strong reducing agent.
- This reaction reduces the carboxylic acid group (\(-COOH\)) to a primary alcohol group (\(-CH_2OH\)).
- **Product X**: The product formed is benzyl alcohol, \( C_6H_5CH_2OH \).

3. **Second Reaction with PBr3**:
- Benzyl alcohol (\( C_6H_5CH_2OH \)) then reacts with phosphorus tribromide (\( PBr_3 \)).
- This reaction replaces the hydroxyl group (\(-OH\)) of the alcohol with a bromine atom (\(-Br\)).
- **Product Y**: The product formed is benzyl bromide, \( C_6H_5CH_2Br \).

4. **Third Reaction with KCN**:
- Benzyl bromide (\( C_6H_5CH_2Br \)) reacts with potassium cyanide (\( KCN \)).
- In this nucleophilic substitution reaction, the bromine atom is replaced by a cyanide group (\(-CN\)).
- **Product Z**: The product formed is benzyl cyanide, \( C_6H_5CH_2CN \).

5. **Final Reaction with LiAlH4**:
- Benzyl cyanide (\( C_6H_5CH_2CN \)) undergoes reduction with \( LiAlH_4 \).
- The nitrile group (\(-CN\)) is reduced to a primary amine (\(-CH_2NH_2\)).
- **Final Product Z**: The final product is benzylamine, \( C_6H_5CH_2CH_2NH_2 \).

### Conclusion:
The final product (Z) after the sequence of reactions is \( C_6H_5CH_2CH_2NH_2 \), which corresponds to option B.