1, 2 dichloroethene is known to exhibit:

Options

A. Optical isomerism
B. Geometrical isomerism
C. Metamerism
D. Tautomerism

Explanation

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

### Step 1: Draw the Structure of 1,2-Dichloroethene
1,2-dichloroethene has the molecular formula C2H2Cl2. The structure can be represented as:

```
Cl Cl
| |
H2C = C
```

### Step 2: Identify the Isomerism
1. **Optical Isomerism**: This type of isomerism occurs when a compound can exist in two forms that are mirror images of each other (enantiomers). For optical isomerism to occur, a molecule must have a chiral center. In the case of 1,2-dichloroethene, there are no chiral centers, so it does not exhibit optical isomerism.

2. **Geometrical Isomerism**: This type of isomerism occurs when there is restricted rotation around a double bond, leading to different spatial arrangements of groups. In 1,2-dichloroethene, we can have two configurations:
- **Cis isomer**: Both chlorine atoms are on the same side of the double bond.
- **Trans isomer**: The chlorine atoms are on opposite sides of the double bond.

Since 1,2-dichloroethene can exist in both cis and trans forms, it exhibits geometrical isomerism.

3. **Metamerism**: This occurs when there are different alkyl groups on either side of a functional group. This is not applicable to 1,2-dichloroethene as it does not have different alkyl groups.

4. **Tautomerism**: This is a type of isomerism involving the migration of a hydrogen atom and a change in bonding. It is not relevant to 1,2-dichloroethene.

### Conclusion
Based on the analysis, 1,2-dichloroethene exhibits geometrical isomerism.

### Final Answer
1,2-dichloroethene is known to exhibit geometrical isomerism.

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