Which type of isomerism is shown by 1,2 - dimethylcyclopropane ?

Options

A. Geometrical isomerism
B. Optical isomerism
C. Position isomerism
D. Conformational isomerism

Answer

To determine the type of isomerism shown by 1,2-dimethylcyclopropane, we can follow these steps:

### Step 1: Identify the Structure
1,2-dimethylcyclopropane has a cyclopropane ring with two methyl groups attached to the first and second carbon atoms of the ring.

### Step 2: Analyze the Isomerism
In this compound, the two methyl groups can be positioned in different orientations relative to each other due to the constraints of the cyclopropane ring.

### Step 3: Determine the Type of Isomerism
1. **Geometrical Isomerism**: This type of isomerism occurs when there are different spatial arrangements of groups around a double bond or a ring structure. In the case of 1,2-dimethylcyclopropane, the two methyl groups can be on the same side (cis) or on opposite sides (trans) of the cyclopropane ring.

2. **Optical Isomerism**: This type of isomerism occurs when a compound can exist in two forms that are mirror images of each other (enantiomers). For 1,2-dimethylcyclopropane, it does not have a chiral center, so it does not exhibit optical isomerism.

3. **Position Isomerism**: This type of isomerism occurs when the position of a functional group changes. In this case, the methyl groups are fixed at the 1 and 2 positions, so this is not applicable.

4. **Conformational Isomerism**: This type of isomerism involves different arrangements of atoms that can be converted into one another by rotation around single bonds. While 1,2-dimethylcyclopropane can have different conformations, the main focus here is on geometrical isomerism.

### Conclusion
Since 1,2-dimethylcyclopropane can exist in cis and trans forms due to the positioning of the methyl groups, it exhibits **geometrical isomerism**.

### Final Answer
The type of isomerism shown by 1,2-dimethylcyclopropane is **Geometrical Isomerism**.

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