Which of the following compunds is capable of showing geometrical, optical and conformational isomerism.

Options

A.
B. `H_(2)C=CH-underset(overset(|)(OH))(C)H-CH_(3)`
C. `CH_(3)-CH=CH-CH_(2)-CH_(2)-OH`
D. `H_(2)C=CH-CH_(2)-OH`

Answer

To determine which of the given compounds is capable of showing geometrical, optical, and conformational isomerism, we will analyze each type of isomerism step by step.

### Step 1: Analyze Geometrical Isomerism
Geometrical isomerism occurs due to the restricted rotation around a double bond or a ring structure, leading to different spatial arrangements of substituents.

1. **Compound 1**: This compound has an allene structure with consecutive double bonds, making it planar. It can show cis-trans isomerism because the substituents can be arranged differently around the double bond.
- **Conclusion**: Shows geometrical isomerism.

2. **Compound 2**: This compound has two identical groups (H) on one side of the double bond, which means it cannot exhibit geometrical isomerism.
- **Conclusion**: Does not show geometrical isomerism.

3. **Compound 3**: This compound has different groups on either side of the double bond (H and CH3 on one side, H and CH2CH2OH on the other). Thus, it can show E/Z isomerism.
- **Conclusion**: Shows geometrical isomerism.

4. **Compound 4**: Similar to Compound 2, it has two identical groups on one side, so it cannot exhibit geometrical isomerism.
- **Conclusion**: Does not show geometrical isomerism.

### Step 2: Analyze Optical Isomerism
Optical isomerism occurs when a compound has chiral centers, leading to non-superimposable mirror images.

1. **Compound 1**: Contains a chiral center (carbon attached to different substituents), hence it can show optical isomerism.
- **Conclusion**: Shows optical isomerism.

2. **Compound 2**: Contains a chiral center as well, thus it can show optical isomerism.
- **Conclusion**: Shows optical isomerism.

3. **Compound 3**: This compound does not have any chiral centers, so it cannot show optical isomerism.
- **Conclusion**: Does not show optical isomerism.

4. **Compound 4**: Similar to Compound 3, it lacks chiral centers, hence does not show optical isomerism.
- **Conclusion**: Does not show optical isomerism.

### Step 3: Analyze Conformational Isomerism
Conformational isomerism arises from the rotation around single bonds, leading to different spatial arrangements (conformers).

1. **Compound 1**: Being planar, it does not have conformational isomerism.
- **Conclusion**: Does not show conformational isomerism.

2. **Compound 2**: This compound can exhibit conformational isomerism due to the presence of different substituents that can adopt staggered or eclipsed conformations.
- **Conclusion**: Shows conformational isomerism.

3. **Compound 3**: This compound also has the ability to show conformational isomerism due to the presence of single bonds allowing rotation.
- **Conclusion**: Shows conformational isomerism.

4. **Compound 4**: This compound does not have any conformational isomerism due to its structure.
- **Conclusion**: Does not show conformational isomerism.

### Final Conclusion
Based on the analysis:
- **Compound 1**: Shows geometrical and optical isomerism but not conformational.
- **Compound 2**: Shows optical and conformational isomerism but not geometrical.
- **Compound 3**: Shows geometrical and conformational isomerism but not optical.
- **Compound 4**: Does not show any of the isomerisms.

Thus, **Compound 2** is the only compound capable of showing geometrical, optical, and conformational isomerism.