Which of the following compounds can be best prepared by Wurtz-reaction ?

Options

A. Iso-butane
B. n-butane
C. n-pentane
D. Iso-pentane

Explanation

To determine which of the given compounds can be best prepared by the Wurtz reaction, we need to analyze the characteristics of the Wurtz reaction and the structures of the compounds provided.

### Step-by-Step Solution:

1. **Understand the Wurtz Reaction**:
The Wurtz reaction involves the coupling of two alkyl halides in the presence of sodium metal (Na) and dry ether. The general reaction can be represented as:
\[ 2 R-X + 2 Na \rightarrow R-R + 2 NaX \]
where \( R \) is the alkyl group and \( X \) is a halogen. This reaction typically produces alkanes with an even number of carbon atoms.

2. **Analyze the Given Compounds**:
The compounds given in the question are:
- Isobutene (C4H8)
- Normal butane (C4H10)
- Normal pentane (C5H12)
- Isopentane (C5H12)

3. **Check Each Compound**:
- **Isobutene (C4H8)**:
- Structure: (CH3)2C=CH2
- It has 4 carbons, but it is an alkene, not an alkane. Therefore, it cannot be prepared by the Wurtz reaction.

- **Normal Butane (C4H10)**:
- Structure: CH3-CH2-CH2-CH3
- It has 4 carbons, which is even. It can be prepared by the Wurtz reaction using 2 moles of butyl chloride (C4H9Cl).

- **Normal Pentane (C5H12)**:
- Structure: CH3-CH2-CH2-CH2-CH3
- It has 5 carbons, which is odd. Therefore, it cannot be prepared by the Wurtz reaction.

- **Isopentane (C5H12)**:
- Structure: (CH3)2CH-CH2-CH3
- It also has 5 carbons, which is odd. Therefore, it cannot be prepared by the Wurtz reaction.

4. **Conclusion**:
After analyzing all the compounds, we can conclude that the only compound that can be best prepared by the Wurtz reaction is **Normal Butane (C4H10)**.

### Final Answer:
**Normal Butane (C4H10)** can be best prepared by the Wurtz reaction.