Total number of conformational isomers obtained by C-C bond rotation of ethane are

Options

A. 2
B. 4
C. 5
D. Infinite

Answer

To determine the total number of conformational isomers obtained by the rotation of the carbon-carbon bond in ethane (C2H6), we can follow these steps:

### Step 1: Understanding Conformational Isomers
Conformational isomers are different spatial arrangements of the same molecule that can be interconverted by rotation around single bonds. In ethane, the relevant bond is the C-C single bond.

**Hint:** Remember that conformational isomers arise from rotations around single bonds, leading to different spatial arrangements.

### Step 2: Visualizing Ethane
Ethane consists of two carbon atoms connected by a single bond, with each carbon atom bonded to three hydrogen atoms. The structure can be represented as:

```
H H
\ /
C - C
/ \
H H
```

**Hint:** Draw the structure of ethane to visualize the atoms and the bond that can rotate.

### Step 3: Rotation Around the C-C Bond
When we rotate the C-C bond, we can obtain different conformations. The most common conformations are:
- **Staggered Conformation:** The hydrogen atoms on adjacent carbons are as far apart as possible.
- **Eclipsed Conformation:** The hydrogen atoms on adjacent carbons are aligned with each other.

**Hint:** Identify the two main types of conformations: staggered (more stable) and eclipsed (less stable).

### Step 4: Counting Conformational Isomers
1. **Staggered Conformation:** There are two staggered conformations:
- Anti (where the two largest groups are opposite each other)
- Gauche (where the two largest groups are adjacent to each other)

2. **Eclipsed Conformation:** There are also two eclipsed conformations:
- Eclipsed (where the hydrogen atoms are directly aligned)
- Eclipsed (where one hydrogen is aligned with a larger group)

Thus, when considering the rotation around the C-C bond, we can see that there are multiple staggered and eclipsed forms.

**Hint:** Analyze the types of staggered and eclipsed conformations to count them accurately.

### Step 5: Conclusion
In total, ethane has:
- 2 staggered conformations (anti and gauche)
- 2 eclipsed conformations

Thus, the total number of conformational isomers obtained by C-C bond rotation of ethane is **3** (considering the unique arrangements).

**Final Answer:** The total number of conformational isomers obtained by C-C bond rotation of ethane is **3**.