Which of the following compounds will exhibit geometrical isomerism?

Options

A. 1, 1- Dipheyenyl -1- propene
B. 1 - Pheyl -2- butene
C. 3-Phenyl -1- butene
D. 2-Phenyl -1- butene

Answer

To determine which of the given compounds exhibits geometrical isomerism, we will analyze each compound step by step.

### Step 1: Analyze 1,1-Diphenylpropene
1. **Structure**: The structure of 1,1-diphenylpropene can be represented as follows:
- Propene has the formula C3H6, with a double bond between the first and second carbon atoms.
- In 1,1-diphenylpropene, both substituents on the first carbon are phenyl groups (C6H5).
- The structure looks like this:
```
Ph Ph
| |
C=C-CH3
```
2. **Isomerism**: Since both substituents on the first carbon are identical (phenyl groups), this compound cannot exhibit geometrical isomerism (cis/trans) because there is no difference in the groups attached to the double bond.

### Step 2: Analyze 1-Phenyl-2-butene
1. **Structure**: The structure of 1-phenyl-2-butene is:
- The double bond is between the second and third carbon atoms.
- The structure can be represented as follows:
```
Ph
|
C=C
| |
CH3 H
```
2. **Isomerism**: In this case, we have:
- On one side of the double bond, there is a phenyl group (Ph) and a hydrogen (H).
- On the other side, there is a methyl group (CH3) and another hydrogen (H).
- This allows for two configurations:
- **Cis**: where the phenyl and methyl groups are on the same side.
- **Trans**: where the phenyl and methyl groups are on opposite sides.
- Therefore, 1-phenyl-2-butene can exhibit geometrical isomerism.

### Step 3: Analyze 3-Phenyl-1-butene
1. **Structure**: The structure of 3-phenyl-1-butene is:
- The double bond is between the first and second carbon atoms.
- The structure can be represented as follows:
```
Ph
|
C=C
| |
H CH2-CH3
```
2. **Isomerism**: In this case:
- The first carbon has a hydrogen (H) and a phenyl group (Ph).
- The second carbon has a hydrogen (H) and a CH2-CH3 group.
- Since the substituents on both sides of the double bond are not different enough to allow for cis/trans configurations, 3-phenyl-1-butene does not exhibit geometrical isomerism.

### Step 4: Analyze 2-Phenyl-1-butene
1. **Structure**: The structure of 2-phenyl-1-butene is:
- The double bond is between the first and second carbon atoms.
- The structure can be represented as follows:
```
C=C
| |
Ph CH3
```
2. **Isomerism**: In this case:
- The first carbon has a phenyl group (Ph) and a hydrogen (H).
- The second carbon has a methyl group (CH3) and a hydrogen (H).
- Similar to 1-phenyl-2-butene, this allows for two configurations (cis/trans) based on the positioning of the phenyl and methyl groups.
- Therefore, 2-phenyl-1-butene can also exhibit geometrical isomerism.

### Conclusion
After analyzing all the compounds, we find that **1-phenyl-2-butene** is the only compound that exhibits geometrical isomerism.