Geometrical isomers :

Options

A. Structural isomers
B. Conformational isomers
C. Configurational isomers
D. None of these

Answer

**Step-by-Step Text Solution:**

1. **Understanding Geometrical Isomers:**
Geometrical isomers are a type of stereoisomer that arise due to restricted rotation around a double bond or a ring structure. They have the same molecular formula and the same structural formula but differ in the spatial arrangement of atoms or groups.

2. **Identifying the Cause of Geometrical Isomerism:**
The key factor that leads to geometrical isomerism is the presence of a double bond (C=C) or a cyclic structure, which restricts the rotation of the atoms or groups attached to the carbon atoms involved in the double bond or the ring.

3. **Examples of Geometrical Isomers:**
A classic example of geometrical isomers can be seen in compounds like 2-butene. In 2-butene, the two isomers are:
- **Cis-2-butene:** Both methyl groups (–CH₃) are on the same side of the double bond.
- **Trans-2-butene:** The methyl groups are on opposite sides of the double bond.

4. **Classification of Isomerism:**
Geometrical isomerism falls under the broader category of configurational isomerism. Isomerism can be classified into two main types:
- **Structural Isomerism:** Where the connectivity of atoms differs.
- **Stereoisomerism:** Where the connectivity is the same, but the spatial arrangement differs.

5. **Types of Stereoisomerism:**
Stereoisomerism can be further divided into:
- **Configurational Isomerism:** Where isomers cannot be interconverted without breaking bonds (e.g., geometrical and optical isomers).
- **Conformational Isomerism:** Where isomers can interconvert freely by rotation around single bonds.

6. **Conclusion:**
Therefore, geometrical isomers are specifically classified as a type of configurational isomerism due to the restricted rotation around double bonds or rings, leading to different spatial arrangements of atoms or groups.

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