Which of the following statements are correct?

Options

A. `2,3,4`- Tribromo pentane has three chiral `C` atoms..
B. Tartaric acid has two asymmetric `C` atoms.
C. `d` and `l` forms of an optically active compound have different specific rotations with opposite signs.
D. Staggered and eclipsed forms of ethane have different stabilities.

Explanation

To determine which statements are correct regarding the isomerism and chirality of certain compounds, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Analyze Statement 1:**
- The statement claims that 2,3,4-tribromopentane has three chiral centers.
- To verify this, we need to draw the structure of 2,3,4-tribromopentane:
- Pentane has five carbon atoms.
- At positions 2, 3, and 4, there are bromine (Br) substituents.
- Identify the chiral centers:
- A carbon atom is chiral if it has four different substituents.
- At carbon 2 (C2): It has Br, CH3, H, and CH2Br (four different groups) → **Chiral**
- At carbon 3 (C3): It has two Br groups (same groups) → **Achiral**
- At carbon 4 (C4): It has Br, H, CH3, and CH2Br (four different groups) → **Chiral**
- Conclusion: There are only **two chiral centers** (C2 and C4), so this statement is **incorrect**.

2. **Analyze Statement 2:**
- The statement claims that tartaric acid has two asymmetric carbon atoms.
- Draw the structure of tartaric acid:
- It has two carbon atoms that are bonded to four different groups.
- Identify the chiral centers:
- Both carbon atoms in tartaric acid have four different substituents (OH, H, COOH, and CH3) → **Both are chiral**.
- Conclusion: This statement is **correct**.

3. **Analyze Statement 3:**
- The statement claims that D and L forms of a compound have different specific rotations.
- D and L forms (enantiomers) of a compound rotate plane-polarized light in opposite directions but have the **same specific rotation** in magnitude.
- Conclusion: This statement is **incorrect**.

4. **Analyze Statement 4:**
- The statement claims that staggered and eclipsed forms of ethane have different stabilities.
- Staggered conformation is more stable than eclipsed due to less steric hindrance and torsional strain.
- The staggered form has a dihedral angle of 60 degrees, while the eclipsed form has a dihedral angle of 0 degrees, leading to increased electron cloud repulsion in the eclipsed form.
- Conclusion: This statement is **correct**.

### Final Conclusion:
- The correct statements are **Statement 2** and **Statement 4**.