`underset((X))("p-Nitro phenol")underset((1))overset((C_2H_5)_2SO_4//NaOH)tounderset((2))overset(Sn//HCl)to(Y)underset((3))overset(NaNO_3//HCl)tounderset((4))overset(C_6H_5OH)to` product is :

Explanation

To solve the given question step by step, we will analyze each reaction involving para-nitrophenol (X) and the reagents provided in the sequence.

### Step 1: Identify the Starting Compound
The starting compound is **p-Nitrophenol (X)**, which has the following structure:
- Hydroxyl group (–OH) at the para position to the nitro group (–NO2).

### Step 2: First Reaction with C2H5)2SO4 and NaOH
In the first step, we treat p-Nitrophenol with **(C2H5)2SO4 (Diethyl sulfate)** in the presence of **NaOH**. This reaction leads to the alkylation of the hydroxyl group:
- The hydroxyl group (–OH) is replaced by an ethoxy group (–O-C2H5).
- The product after this step (let's call it **Y**) will be **p-Nitrophenyl ethyl ether**.

**Product after Step 1:**
- Structure: O-C2H5 at the para position to –NO2.

### Step 3: Second Reaction with Sn and HCl
In the second step, we treat the product from Step 1 (Y) with **Sn and HCl**. This reaction reduces the nitro group (–NO2) to an amino group (–NH2):
- The nitro group is reduced to an amine.

**Product after Step 2:**
- Structure: O-C2H5 at the para position to –NH2.

### Step 4: Third Reaction with NaNO2 and HCl
In the third step, we treat the product from Step 2 with **NaNO2 and HCl**. This reaction converts the amino group (–NH2) into a diazonium salt (–N2+):
- The amino group is transformed into a diazonium ion.

**Product after Step 3:**
- Structure: O-C2H5 at the para position to –N2+.

### Step 5: Fourth Reaction with C6H5OH
In the final step, we react the diazonium salt with **C6H5OH (Phenol)**. This reaction leads to the formation of an azo compound:
- The diazonium ion couples with phenol to form an azo compound.

**Final Product:**
- Structure: O-C2H5 at the para position to –N=N–OH (the azo group).

### Summary of the Final Product
The final product is an azo compound with an ethoxy group at the para position and a hydroxyl group attached to the azo linkage.

### Final Answer:
The product formed after the complete reaction sequence is **p-Ethoxyphenyl azo phenol**.

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