**Structural Isomerism**

Structural isomerism refers to the phenomenon where compounds have the same molecular formula but differ in the arrangement of atoms within the molecule. In the case of 2,3-dichlorobutane, it exhibits structural isomerism.

**Explanation:**

1. **Definition of Isomerism:** Isomerism is the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in different chemical and physical properties.

2. **Molecular Formula of 2,3-dichlorobutane:** The molecular formula of 2,3-dichlorobutane is C4H8Cl2, indicating that it contains 4 carbon atoms, 8 hydrogen atoms, and 2 chlorine atoms.

3. **Structural Isomerism:** This type of isomerism occurs when compounds have the same molecular formula but differ in the arrangement of atoms within the molecule.

4. **Structural Isomers of 2,3-dichlorobutane:** Since 2,3-dichlorobutane has the molecular formula C4H8Cl2, we can examine the different possibilities for the arrangement of atoms within the molecule.

a. **Isomer 1: 1,2-Dichlorobutane** - In this isomer, the two chlorine atoms are attached to the carbon atoms at positions 1 and 2, respectively.

b. **Isomer 2: 1,3-Dichlorobutane** - In this isomer, the two chlorine atoms are attached to the carbon atoms at positions 1 and 3, respectively.

c. **Isomer 3: 2,3-Dichlorobutane** - In this isomer, the two chlorine atoms are attached to the carbon atoms at positions 2 and 3, respectively.

5. **Different Properties:** These different structural isomers of 2,3-dichlorobutane will exhibit different chemical and physical properties due to their distinct arrangements of atoms.

- **Physical Properties:** Physical properties such as boiling point, melting point, density, and solubility may vary between the isomers due to differences in molecular structure.

- **Chemical Properties:** The reactivity and behavior of the isomers may differ in various chemical reactions due to differences in the arrangement of functional groups and their proximity to each other.

6. **Conclusion:** Therefore, 2,3-dichlorobutane exhibits structural isomerism because it has multiple structural isomers with the same molecular formula (C4H8Cl2) but different arrangements of atoms within the molecule.

2. optical isomerism...am i right?