Which of the following compounds will show geometrical isomerism -

Options

A. 2- Butyne
B. 2-Pentene
C. 2- Methylpropene
D. 2-Methyl -2-Butene

Answer

To determine which of the given compounds shows geometrical isomerism, we will analyze each option based on the criteria for geometrical isomerism. Geometrical isomerism occurs in compounds where there is restricted rotation around a double bond or in cyclic compounds, leading to different spatial arrangements of substituents.

### Step-by-Step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism (cis-trans isomerism) occurs when there is restricted rotation around a double bond (C=C) or in cyclic structures. For geometrical isomers, the substituents attached to the double-bonded carbons must be different.

2. **Analyzing Option 1: 2-butyne**:
- Structure: CH3-C≡C-CH3 (triple bond)
- A triple bond does not allow for geometrical isomerism because the carbon atoms involved in the triple bond cannot exhibit cis or trans configurations.
- **Conclusion**: Does not show geometrical isomerism.

3. **Analyzing Option 2: 2-pentyne**:
- Structure: CH3-C≡C-CH2-CH3
- Similar to 2-butyne, a triple bond is present, which restricts the possibility of geometrical isomerism.
- **Conclusion**: Does not show geometrical isomerism.

4. **Analyzing Option 3: 2-methylpropene**:
- Structure: CH2=C(CH3)-CH3
- In this case, the double bond is between two carbon atoms, but both substituents on one side of the double bond are the same (two CH3 groups). Hence, it cannot exhibit cis or trans configurations.
- **Conclusion**: Does not show geometrical isomerism.

5. **Analyzing Option 4: 2-methylbutene**:
- Structure: CH3-CH=C(CH3)-CH3
- Here, the double bond is between two carbon atoms, and the substituents on each carbon of the double bond are different (CH3 and H on one side, CH3 and H on the other). This allows for cis (both CH3 on the same side) and trans (CH3 on opposite sides) configurations.
- **Conclusion**: Shows geometrical isomerism.

### Final Answer:
The compound that shows geometrical isomerism is **Option 4: 2-methylbutene**.