Compound (X) of molecular formula `C_4H_8` takes up one equivalent of hydrogen in presence of Pt to form another compound (Y),(X) on ozonolysis gives acetaldehyde as the only product. Compound (X) is

Options

A. `CH_3-CH_2-CH=CH_2`
B. `CH_3-CH=CH-CH_3`
C. Cyclobutane
D. Cyclobutene

Answer

To solve the problem, we need to determine the structure of compound (X) with the molecular formula C₄H₈, which undergoes hydrogenation to form compound (Y) and gives acetaldehyde upon ozonolysis.

### Step-by-Step Solution:

1. **Determine the Degree of Unsaturation (DU)**:
- The formula for calculating the degree of unsaturation (DU) is:
\[ \text{DU} = C + 1 - \frac{H}{2} - \frac{X}{2} + \frac{N}{2} \]
- For C₄H₈:
- C = 4
- H = 8
- X (halogens) = 0
- N (nitrogens) = 0
- Plugging in the values:
\[ \text{DU} = 4 + 1 - \frac{8}{2} = 4 + 1 - 4 = 1 \]
- This indicates that there is either one double bond or one ring in the structure.

**Hint**: The degree of unsaturation helps us identify the presence of rings or double bonds in the compound.

2. **Identify Compound (X)**:
- Since DU = 1, compound (X) could be an alkene or a cyclic compound.
- The molecular formula C₄H₈ suggests it could be butene (either 1-butene or 2-butene).

3. **Hydrogenation of Compound (X)**:
- Compound (X) takes up one equivalent of hydrogen in the presence of platinum (Pt), indicating it is an alkene.
- The hydrogenation of an alkene will yield an alkane. Thus, if (X) is butene, it would convert to butane (C₄H₁₀).

4. **Ozonolysis of Compound (X)**:
- The ozonolysis of compound (X) gives acetaldehyde (CH₃CHO) as the only product.
- Acetaldehyde is a product of breaking a double bond in a specific manner. For butenes, ozonolysis typically yields two moles of acetaldehyde if the double bond is in the correct position.

5. **Determine the Structure of Compound (X)**:
- The only butene that can yield two moles of acetaldehyde upon ozonolysis is 2-butene (CH₃-CH=CH-CH₃).
- The ozonolysis of 2-butene results in:
\[ \text{Ozonolysis of 2-butene} \rightarrow 2 \times \text{Acetaldehyde} \]

6. **Conclusion**:
- Therefore, compound (X) is **2-butene** (C₄H₈).

### Final Answer:
Compound (X) is **2-butene**.

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