Which of the following can not exhibit geometrical isomerism

Options

A. `a_(2)C=Cb_(2)`
B. `abC=Cde`
C. `abC=Cab`
D. abC=Cda

Answer

To determine which of the given compounds cannot exhibit geometrical isomerism, we need to understand the conditions required for geometrical isomerism to occur.

### Step-by-Step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism occurs in compounds with a carbon-carbon double bond (C=C) where the two carbon atoms are bonded to different groups. The two main types of geometrical isomerism are cis-trans isomerism and E-Z isomerism.

2. **Identifying the Conditions**:
- For geometrical isomerism to be possible, the following conditions must be met:
- There must be a carbon-carbon double bond.
- Each carbon of the double bond must be attached to two different substituents (groups). If both substituents on one carbon are the same, geometrical isomerism cannot occur.

3. **Analyzing the Options**:
- Let's consider the four options provided:
- **Option A**: C=C with two identical groups (e.g., A and A).
- **Option B**: C=C with one A and one B on one carbon, and one B and one E on the other carbon.
- **Option C**: C=C with one A and one B on one carbon, and one A and one B on the other carbon.
- **Option D**: C=C with one A, one B, and one D on one carbon and one E on the other carbon.

4. **Evaluating Each Option**:
- **Option A**: Since both groups on one carbon are the same (A and A), this compound cannot exhibit geometrical isomerism.
- **Option B**: This compound has different groups on both carbons (A, B on one side and B, E on the other), allowing for geometrical isomerism.
- **Option C**: This compound also has the same groups (A and B) on both sides, allowing for geometrical isomerism.
- **Option D**: This compound has all different groups (A, B, D on one side and E on the other), allowing for geometrical isomerism.

5. **Conclusion**:
- The only option that cannot exhibit geometrical isomerism is **Option A**, where both substituents on one carbon are identical.

### Final Answer:
**Option A** cannot exhibit geometrical isomerism.