Conformations are different arrangements of atoms that are interconverted by rotation about single bond.
In eclipsed conformation, the C-H bond on-one carbon is directly aligned with C-H bond on the adjacent carbon.
In staggered conformation, the c H bond on one carbon biseçt, the H G H bond angle on adjacent carbon.
The angle that separates a bond on one atom from a bond on a adjacent atom is called a dihedral angle.
A staggered conformation with two larger groups `180^(@)` from each other is called anti. A staggered conformation with two larger group `60^(@)` from each other is called gauche.
Which of the following conformer of butane has minimum,energy?

Options

A.
B.
C.
D.

Explanation

To determine which conformer of butane has the minimum energy, we need to analyze the different conformations: eclipsed and staggered.

### Step-by-Step Solution:

1. **Understanding Conformations**:
- Conformations are different spatial arrangements of atoms in a molecule that can be interconverted by rotation around single bonds.
- In butane, we can have different conformers based on the arrangement of the hydrogen atoms and the two methyl (CH₃) groups.

2. **Eclipsed vs. Staggered Conformations**:
- **Eclipsed Conformation**: In this arrangement, the C-H bonds on one carbon are directly aligned with the C-H bonds on the adjacent carbon. This alignment leads to torsional strain due to repulsion between the electron clouds of the bonds.
- **Staggered Conformation**: Here, the C-H bonds on one carbon bisect the H-H bond angle on the adjacent carbon. This arrangement minimizes electron repulsion and is generally more stable.

3. **Dihedral Angle**:
- The dihedral angle is the angle between the planes formed by two sets of atoms. In staggered conformations, the dihedral angles can be 60° (gauche) or 180° (anti).

4. **Types of Staggered Conformations**:
- **Anti Conformation**: This is when the two larger groups (e.g., CH₃) are 180° apart. This arrangement is the most stable due to minimal steric hindrance.
- **Gauche Conformation**: This occurs when the two larger groups are 60° apart. This arrangement is less stable than the anti conformation due to increased steric strain.

5. **Comparing Energies**:
- The anti conformation has the lowest energy and is the most stable due to the optimal arrangement of the bulky groups.
- The gauche conformation has higher energy due to steric interactions between the larger groups.

6. **Conclusion**:
- Among the conformers of butane, the anti conformation (where the two CH₃ groups are 180° apart) has the minimum energy and is thus the most stable conformer.

### Final Answer:
The conformer of butane that has minimum energy is the **anti conformation**.