In which of the following structures C-3 is not a chiral center ?

Options

A.
B.
C.
D.

Explanation

To determine which of the given structures has C-3 as a non-chiral center, we need to analyze the chirality of C-3 in each structure. A carbon atom is considered a chiral center if it is bonded to four different groups. If there is a plane of symmetry in the molecule, then the carbon is not a chiral center.

### Step-by-Step Solution:

1. **Identify the Structures**: We have four structures labeled A, B, C, and D. We need to analyze C-3 in each of these structures.

2. **Analyze Structure A**:
- Structure A has the following groups attached to C-3: CH3, HOH, HBr, and HBr.
- Since all four groups are different (two HBr groups are identical but are counted as one), C-3 does not have a plane of symmetry.
- **Conclusion**: C-3 is a chiral center in structure A.

3. **Analyze Structure B**:
- Structure B has the following groups attached to C-3: CH3, HBr, HOH, and HBr.
- Here, we can see that there is a plane of symmetry that divides the molecule into two identical halves.
- **Conclusion**: C-3 is not a chiral center in structure B.

4. **Analyze Structure C**:
- Structure C has the following groups attached to C-3: CH3, HBr, HOH, and HBr.
- Similar to structure B, there is a plane of symmetry present in this structure as well.
- **Conclusion**: C-3 is not a chiral center in structure C.

5. **Analyze Structure D**:
- Structure D has the following groups attached to C-3: CH3, HBr, HBr, and HOH.
- In this case, all four groups attached to C-3 are different from each other, and there is no plane of symmetry.
- **Conclusion**: C-3 is a chiral center in structure D.

### Final Answer:
C-3 is not a chiral center in structures **B** and **C**.