Identify (Z) in the following series.
`Ethanol overset(PBr_(3))to (X) overset(Alc.//KOH)to (Y) overset((i)H_(2)SO_(4)//("Room temp")) underset((ii)(H_(2)O,Heat))to(Z)`

Options

A. `CH_(3)CH_(2)-OH`
B. `CH_(2)=CH_(2)`
C. `CH_(3)CH_(2)-o-CH_(2)CH_(3)`
D. `CH_(3)CH_(2)-O-SO_(3)H`

Explanation

To identify compound (Z) in the given reaction series, we will analyze each step of the reactions systematically.

### Step 1: Reaction of Ethanol with PBr3
- **Starting Compound**: Ethanol (C₂H₅OH)
- **Reaction**: Ethanol reacts with phosphorus tribromide (PBr₃).
- **Product (X)**: The hydroxyl group (OH) in ethanol is replaced by a bromine atom (Br), resulting in bromoethane (C₂H₅Br).

**Chemical Equation**:
\[ \text{C}_2\text{H}_5\text{OH} + \text{PBr}_3 \rightarrow \text{C}_2\text{H}_5\text{Br} + \text{HBr} + \text{H}_3\text{PO}_3 \]

### Step 2: Reaction of Bromoethane with Alcoholic KOH
- **Starting Compound**: Bromoethane (C₂H₅Br)
- **Reaction**: Bromoethane undergoes elimination when treated with alcoholic KOH.
- **Product (Y)**: The reaction removes HBr, leading to the formation of ethene (C₂H₄).

**Chemical Equation**:
\[ \text{C}_2\text{H}_5\text{Br} + \text{KOH (alc)} \rightarrow \text{C}_2\text{H}_4 + \text{HBr} + \text{KBr} \]

### Step 3: Reaction of Ethene with Sulfuric Acid
- **Starting Compound**: Ethene (C₂H₄)
- **Reaction**: Ethene reacts with sulfuric acid (H₂SO₄) at room temperature, followed by hydrolysis (addition of water with heat).
- **Product (Z)**: The addition of H₂SO₄ introduces a proton (H⁺) to one carbon and the bisulfate ion (HSO₄⁻) to the other carbon. Upon hydrolysis, the bisulfate is replaced by a hydroxyl group (OH), resulting in ethanol (C₂H₅OH).

**Chemical Equation**:
1. Addition of H₂SO₄:
\[ \text{C}_2\text{H}_4 + \text{H}_2\text{SO}_4 \rightarrow \text{C}_2\text{H}_5\text{OSO}_3\text{H} \]
2. Hydrolysis:
\[ \text{C}_2\text{H}_5\text{OSO}_3\text{H} + \text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_5\text{OH} + \text{H}_2\text{SO}_4 \]

### Conclusion
The final product (Z) after the complete series of reactions is ethanol (C₂H₅OH).

### Answer:
**(Z) is Ethanol (C₂H₅OH)**

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