Which of the following structures represents a chiral compound?

Options

A.
B.
C.
D.

Explanation

To determine which of the given structures represents a chiral compound, we need to identify the presence of a chiral center in each structure. A chiral center is typically a carbon atom that is bonded to four different substituents.

Here’s a step-by-step solution:

### Step 1: Understand the Definition of Chirality
Chirality in chemistry refers to a property of a molecule that makes it non-superimposable on its mirror image. A chiral compound must have at least one chiral center, which is usually a carbon atom bonded to four different groups.

**Hint:** Remember that for a carbon to be a chiral center, it must have four distinct substituents.

### Step 2: Analyze Each Structure
We will analyze each of the given structures one by one to identify the presence of a chiral center.

1. **Structure 1:**
- Check the carbon atoms for substituents.
- If a carbon has two identical groups (e.g., two methyl groups), it cannot be a chiral center.
- In this structure, we find that no carbon has four different substituents.

**Hint:** Look for identical groups on the carbon atoms.

2. **Structure 2:**
- Again, check each carbon atom.
- If any carbon has two identical substituents, it cannot be a chiral center.
- In this structure, we also find that no carbon has four different substituents.

**Hint:** Identify if any carbon has two identical groups.

3. **Structure 3:**
- Repeat the analysis for this structure.
- Check for identical substituents on the carbon atoms.
- This structure also lacks a carbon with four different substituents.

**Hint:** Ensure to check all carbon atoms for uniqueness in substituents.

4. **Structure 4:**
- Examine the substituents on the carbon atoms.
- Here, we find a carbon that has four different substituents: hydrogen (H), methyl (CH3), hydroxyl (OH), and another group.
- This carbon qualifies as a chiral center.

**Hint:** Look for a carbon with four distinct groups to identify chirality.

### Step 3: Conclusion
After analyzing all the structures, we conclude that **Structure 4** contains a chiral center because it has four different substituents attached to one of its carbon atoms. Therefore, Structure 4 represents a chiral compound.

**Final Answer:** Structure 4 is the chiral compound.