Which alkane cannot be be produced using only one type of alkyl halide in Wurtz reaction?

Options

A. `CH_3-CH_3`
B. `CH_3CH_2CH_2CH_3`
C. `CH_3CH_2CH_2CH_2CH_3`
D.

Answer

To determine which alkane cannot be produced using only one type of alkyl halide in the Wurtz reaction, we need to analyze the options given: ethane, butane, pentane, and 2,3-dimethylbutane.

### Step-by-Step Solution:

1. **Understanding the Wurtz Reaction**:
The Wurtz reaction involves the coupling of two alkyl halides in the presence of sodium (Na) to form an alkane. The general reaction is:
\[ 2 \text{R-X} + 2 \text{Na} \rightarrow \text{R-R} + 2 \text{NaX} \]
Here, R represents the alkyl group, and X is the halogen.

2. **Identifying Symmetrical vs. Unsymmetrical Alkanes**:
- Symmetrical alkanes can be formed from two identical alkyl halides.
- Unsymmetrical alkanes require different alkyl halides or cannot be formed from just one type.

3. **Analyzing Each Option**:
- **Ethane (C2H6)**:
- Can be produced using 2 moles of CH3Cl or CH3Br:
\[ 2 \text{CH}_3\text{Cl} + 2 \text{Na} \rightarrow \text{C}_2\text{H}_6 + 2 \text{NaCl} \]
- **Conclusion**: Ethane can be produced.

- **Butane (C4H10)**:
- Can be produced using 2 moles of CH3CH2Cl:
\[ 2 \text{CH}_3\text{CH}_2\text{Cl} + 2 \text{Na} \rightarrow \text{C}_4\text{H}_{10} + 2 \text{NaCl} \]
- **Conclusion**: Butane can be produced.

- **Pentane (C5H12)**:
- Cannot be produced using only one type of alkyl halide. If we try to use CH3(CH2)3Cl (which is a 4-carbon chain), we cannot obtain a 5-carbon chain (pentane) because it would require a combination of two different alkyl halides.
- **Conclusion**: Pentane cannot be produced.

- **2,3-Dimethylbutane (C5H12)**:
- Can be produced using 2 moles of 2-bromobutane (CH3CHBrCH3):
\[ 2 \text{CH}_3\text{C}(\text{Br})\text{HCH}_3 + 2 \text{Na} \rightarrow \text{C}_5\text{H}_{12} + 2 \text{NaBr} \]
- **Conclusion**: 2,3-Dimethylbutane can be produced.

4. **Final Conclusion**:
The only alkane that cannot be produced using only one type of alkyl halide in the Wurtz reaction is **pentane**.

### Answer:
**Pentane cannot be produced using only one type of alkyl halide in the Wurtz reaction.**