What is the major product (Z) of the reaction?
`PhCOOH underset(H_2SO_4)overset(HNO_3)(rarr) overset(Sn//HCl)(rarr)underset(HCl)overset(NaNO_2)(rarr)underset(Delta)overset(H_2O)(rarr)`

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Answer

To determine the major product (Z) of the given reaction sequence, we will follow the steps outlined in the transcript.

### Step-by-Step Solution:

1. **Starting Material**: The reaction begins with benzoic acid (PhCOOH).

2. **Nitration Reaction**:
- The benzoic acid is treated with a mixture of concentrated nitric acid (HNO3) and sulfuric acid (H2SO4).
- This mixture serves as a nitrating agent, where H2SO4 generates the nitronium ion (NO2^+) which acts as an electrophile.
- The electron-rich benzene ring of benzoic acid will undergo electrophilic aromatic substitution.
- Since benzoic acid has a carboxylic acid group (-COOH) that is electron-withdrawing, it directs the incoming nitro group (NO2) to the meta position relative to itself.

3. **Formation of Nitrobenzoic Acid**:
- The major product after nitration will be meta-nitrobenzoic acid (m-NO2PhCOOH).

4. **Reduction of Nitro Group**:
- The next step involves treating the meta-nitrobenzoic acid with tin (Sn) and hydrochloric acid (HCl).
- This is a reduction reaction where the nitro group (NO2) is converted to an amine group (NH2).
- The product after this step will be meta-aminobenzoic acid (m-NH2PhCOOH).

5. **Formation of Diazonium Salt**:
- The meta-aminobenzoic acid is then treated with sodium nitrite (NaNO2) in the presence of hydrochloric acid (HCl) at 0°C.
- This reaction forms a diazonium salt (m-N2ClPhCOOH).

6. **Hydrolysis of Diazonium Salt**:
- Finally, the diazonium salt is treated with water (H2O) under heat (Δ).
- The nucleophilic water will attack the diazonium group, replacing it with a hydroxyl group (OH).
- The major product of this step will be meta-hydroxybenzoic acid (m-OHPhCOOH).

### Final Product:
The major product (Z) of the entire reaction sequence is **meta-hydroxybenzoic acid**.

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