What is Z in the following sequence of reactions?
`Z overset(PCl_(3))toX overset(alc.KOH)to Y underset((ii)H_(2)O boil)overset((i)Conc.H_(2)SO_(4))toZ`

Options

A. `CH_(3)CH_(2)CH_(2)OH`
B. `CH_(3)CHOHCH_(3)`
C. `(CH_(3)CH_(2))_(2)CHOH`
D. `CH_(3)-CH=CH_(2)`

Answer

To determine what Z is in the given sequence of reactions, we will analyze each step of the reaction sequence carefully.

### Step-by-Step Solution:

1. **Identify the starting compound (Z)**:
Let's denote the starting compound as Z. The question provides a sequence of reactions, and we need to identify what Z is.

2. **Reaction with PCl₃**:
The first reaction involves Z reacting with phosphorus trichloride (PCl₃). PCl₃ typically converts alcohols to alkyl chlorides. Therefore, Z must be an alcohol.

3. **Formation of X**:
When Z reacts with PCl₃, it forms X, which is an alkyl chloride. The general reaction can be represented as:
\[ Z + PCl₃ \rightarrow X \]
Here, the hydroxyl group (-OH) in Z is replaced by a chlorine atom (-Cl) in X.

4. **Reaction with alcoholic KOH**:
The next step involves X reacting with alcoholic KOH. Alcoholic KOH is a strong base and is used for elimination reactions. In this case, X will undergo elimination to form an alkene (Y). The reaction can be represented as:
\[ X \overset{alc.KOH}{\rightarrow} Y \]
This suggests that X must be a secondary or tertiary alkyl chloride to facilitate elimination.

5. **Formation of Y**:
The product Y is an alkene formed from the elimination of HCl from X.

6. **Reaction with concentrated H₂SO₄**:
The next step involves Y reacting with concentrated sulfuric acid (H₂SO₄). This reaction typically leads to the formation of an alkyl hydrogen sulfate, which can then be hydrolyzed to regenerate the alcohol. The reaction can be represented as:
\[ Y \overset{conc.H₂SO₄}{\rightarrow} Z' \]
Here, Z' is a compound that can be hydrolyzed.

7. **Hydrolysis with water**:
Finally, Z' undergoes hydrolysis when treated with water (boiling), leading to the regeneration of Z:
\[ Z' + H₂O \rightarrow Z \]
This indicates that Z is the same as the original alcohol we started with.

### Conclusion:
Based on the sequence of reactions and the transformations involved, we can conclude that Z is an alcohol that can be converted to an alkyl chloride, then to an alkene, and finally back to the original alcohol through hydrolysis.

### Final Answer:
Z is an alcohol that can undergo the described reactions.