In the reaction
`CH_(3)CH_(2)C Cl_(2)CH_(3)overset(x)rarrCH_(3)C-=C CH_(3)` the reagent X is -

Options

A. `KOH // C_(2)H_(5)OH`
B. Zn
C. `HCl//H_(2)O`
D. Na

Answer

To determine the reagent \( X \) in the reaction

\[ \text{CH}_3\text{CH}_2\text{CCl}_2\text{CH}_3 \xrightarrow{x} \text{CH}_3\text{C} \equiv \text{C}\text{CH}_3 \]

we need to analyze the transformation occurring in the reaction.

### Step-by-Step Solution:

1. **Identify the Starting Material**: The starting compound is 1,2-dichlorobutane (CH₃CH₂CCl₂CH₃), which contains two chlorine atoms on adjacent carbons. This structure is known as a geminal dihalide.

2. **Recognize the Target Compound**: The target compound is 2-butyne (CH₃C≡CCH₃), which is an alkyne. The conversion from a geminal dihalide to an alkyne typically involves the elimination of two halogen atoms and two hydrogen atoms.

3. **Determine the Type of Reaction**: The reaction is an elimination reaction, specifically an E2 elimination, where a strong base removes a proton (H⁺) and a leaving group (Cl⁻) simultaneously.

4. **Identify the Reagent**: For the elimination to occur, a strong base is required. In this case, potassium hydroxide (KOH) is a suitable reagent. It can abstract the hydrogen atoms adjacent to the carbon atoms bearing the chlorine atoms.

5. **Write the Reaction Mechanism**:
- The base (KOH) abstracts a proton from the carbon adjacent to the carbon with the first Cl atom, forming a double bond and releasing one Cl atom.
- The base then abstracts another proton from the adjacent carbon, leading to the formation of a triple bond and releasing the second Cl atom.

6. **Final Reaction**: The overall transformation can be summarized as:
\[ \text{CH}_3\text{CH}_2\text{CCl}_2\text{CH}_3 \xrightarrow{\text{KOH}} \text{CH}_3\text{C} \equiv \text{C}\text{CH}_3 \]

### Conclusion:
The reagent \( X \) is **KOH** (potassium hydroxide).

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