Among the three conformations of ethane, the order of stability follows the sequence

Options

A. Eclipsed `gt` gauche `gt` staggered
B. Eclipsed `gt` staggered `gt` gauche
C. Staggered `gt` gauche `gt` eclipsed
D. Gauche `gt` staggered `gt` eclipsed

Explanation

To determine the order of stability among the three conformations of ethane, we need to analyze the different conformations: staggered, eclipsed, and gauche. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Conformations
Ethane (C2H6) can adopt three main conformations when viewed along the C-C bond:
1. **Staggered Conformation**: The hydrogen atoms on adjacent carbons are positioned as far apart as possible.
2. **Eclipsed Conformation**: The hydrogen atoms on adjacent carbons are aligned with each other, leading to maximum repulsion.
3. **Gauche Conformation**: This is a specific type of staggered conformation where the two larger groups (in this case, hydrogen atoms) are adjacent to each other, but still staggered.

### Step 2: Analyze Stability
- **Staggered Conformation**: This is the most stable conformation because the hydrogen atoms are as far apart as possible, minimizing steric hindrance and torsional strain.
- **Gauche Conformation**: This conformation is less stable than staggered but more stable than eclipsed. The hydrogen atoms are still staggered, but they are closer together, leading to some steric strain.
- **Eclipsed Conformation**: This is the least stable conformation due to the maximum steric hindrance and torsional strain, as the hydrogen atoms are aligned with each other.

### Step 3: Order of Stability
Based on the analysis:
1. **Staggered** (most stable)
2. **Gauche**
3. **Eclipsed** (least stable)

Thus, the order of stability of the conformations of ethane is:
**Staggered > Gauche > Eclipsed**

### Final Answer
The correct sequence of stability among the three conformations of ethane is: **Staggered > Gauche > Eclipsed**.

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