Which of the following conformations of butane is most stable?

Options

A. Skew
B. Anti
C. Gauche
D. Eclipsed

Explanation

To determine which conformation of butane is the most stable, we will analyze the different conformations of butane and evaluate their stability based on steric interactions between the bulky groups (methyl groups).

### Step-by-Step Solution:

1. **Identify the Structure of Butane**:
Butane has the molecular formula \( C_4H_{10} \) and can be represented as:
\[ CH_3-CH_2-CH_2-CH_3 \]

2. **Understand Conformational Isomers**:
Butane can adopt various conformations due to rotation around the carbon-carbon single bonds. The main conformations include:
- **Eclipsed**: Bulky groups are aligned with each other, leading to maximum steric hindrance.
- **Staggered**: Bulky groups are positioned as far apart as possible, minimizing steric hindrance.
- **Gauche**: A staggered conformation where bulky groups are 60° apart.
- **Anti**: A staggered conformation where bulky groups are 180° apart.

3. **Evaluate Stability**:
- **Eclipsed Conformation**: This is the least stable due to maximum steric repulsion between the bulky \( CH_3 \) groups.
- **Gauche Conformation**: This has some steric hindrance due to the \( CH_3 \) groups being 60° apart, making it less stable than staggered forms.
- **Anti Conformation**: Here, the \( CH_3 \) groups are 180° apart, resulting in minimal steric repulsion, making it the most stable conformation.

4. **Conclusion**:
Based on the analysis of steric interactions:
- The **Anti conformation** of butane is the most stable due to the least steric hindrance between the bulky \( CH_3 \) groups.

### Final Answer:
The most stable conformation of butane is the **Anti conformation**.

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