2-butene shows geometrical isomerism due to:

Options

A. Restricted rotation about double bond
B. Free rotation about double bond
C. free rotation about single bond
D. Chiral carbon

Answer

To solve the question of why 2-butene shows geometrical isomerism, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of 2-Butene**:
- The molecular formula of 2-butene is C4H8. Its structure can be represented as CH3-CH=CH-CH3, where there is a double bond between the second and third carbon atoms.

2. **Understand Hybridization**:
- The carbon atoms involved in the double bond (C2 and C3) are sp² hybridized. This means that each of these carbon atoms has three sp² hybrid orbitals and one unhybridized p orbital.

3. **Analyze the Geometry**:
- Due to sp² hybridization, the substituents attached to these carbon atoms lie in the same plane. The double bond creates a rigid structure that does not allow for free rotation.

4. **Recognize the Restriction of Rotation**:
- The presence of the double bond means that the rotation around the bond is restricted. Unlike single bonds, which allow for free rotation, double bonds maintain a specific orientation of the attached groups.

5. **Identify Geometrical Isomers**:
- Because of the restricted rotation, 2-butene can exist in two geometrical forms:
- **Cis Isomer**: The two methyl (CH3) groups are on the same side of the double bond.
- **Trans Isomer**: The two methyl groups are on opposite sides of the double bond.

6. **Conclusion**:
- Therefore, 2-butene exhibits geometrical isomerism due to the restricted rotation about the double bond.

### Final Answer:
2-butene shows geometrical isomerism due to **restricted rotation about the double bond**.

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