Which of the following statements is correct?

Options

A. Ethane can have only three conformations.
B. In staggered conformation, the hydrogen atoms of the nearer methyl group just eclipse the hydrogen atoms of the farther methyl group.
C. The staggered conformer is more stable than the eclipsed conformer.
D. The staggered and eclipsed conformers of ethane can be isolated in the pure form.

Explanation

To determine which statement regarding ethane is correct, let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Ethane can have only three conformations.

**Analysis:** Ethane (C2H6) has a free rotation around the C-C bond, which allows for an infinite number of conformations. However, the most commonly discussed conformations are staggered and eclipsed. Therefore, this statement is incorrect.

### Step 2: Analyze the second statement
**Statement:** In staggered conformation, the hydrogen atom of the near methyl group just eclipses the hydrogen atom of the farther methyl group.

**Analysis:** In the staggered conformation, the hydrogen atoms are positioned as far apart as possible, minimizing repulsion. The description given suggests an eclipsed arrangement rather than staggered. Therefore, this statement is also incorrect.

### Step 3: Analyze the third statement
**Statement:** The staggered conformer is more stable than the eclipsed conformer.

**Analysis:** This statement is correct. The staggered conformation is indeed more stable than the eclipsed conformation due to reduced torsional strain. In the eclipsed conformation, the hydrogen atoms are closer together, leading to increased repulsion and instability.

### Step 4: Analyze the fourth statement
**Statement:** The staggered and eclipsed conformers of ethane can be isolated in pure form.

**Analysis:** The energy difference between staggered and eclipsed conformations is relatively small (about 12.55 kJ/mol). At room temperature, thermal energy allows for interconversion between these conformations, making it impossible to isolate them in pure form. Thus, this statement is incorrect.

### Conclusion
After analyzing all the statements, the correct statement is:
**The staggered conformer is more stable than the eclipsed conformer.**