Which of the following Alkane can not be prepared by hydrogenation of Olefine-

Options

A. Propane
B. Iso butane
C. Iso pentane
D. Neo pentane

Answer

To determine which alkane cannot be prepared by hydrogenation of olefins, let's analyze the options provided.

### Step 1: Understand Hydrogenation
Hydrogenation is a chemical reaction that involves the addition of hydrogen (H₂) to a compound, typically alkenes (olefins), to convert them into alkanes. This process requires the presence of a catalyst, usually a metal like palladium, platinum, or nickel.

### Step 2: Analyze Each Option
1. **Propane (C₃H₈)**:
- Propane can be obtained from the hydrogenation of propene (C₃H₆).
- Reaction: C₃H₆ + H₂ → C₃H₈
- Conclusion: Propane can be prepared by hydrogenation.

2. **Isobutane (C₄H₁₀)**:
- Isobutane can be obtained from the hydrogenation of isobutylene (C₄H₈).
- Reaction: C₄H₈ + H₂ → C₄H₁₀
- Conclusion: Isobutane can be prepared by hydrogenation.

3. **Isopentane (C₅H₁₂)**:
- Isopentane can be obtained from the hydrogenation of isopentylene (C₅H₁₀).
- Reaction: C₅H₁₀ + H₂ → C₅H₁₂
- Conclusion: Isopentane can be prepared by hydrogenation.

4. **Neopentane (C₅H₁₂)**:
- Neopentane has the structure (CH₃)₄C, which means it has a central carbon atom bonded to four methyl groups (CH₃).
- This structure does not have any double bonds (alkenes) that can be hydrogenated.
- Conclusion: Neopentane cannot be prepared by hydrogenation of olefins because it lacks the necessary double bond.

### Final Answer
The alkane that cannot be prepared by hydrogenation of olefins is **Neopentane (option 4)**.

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