The toal number of structural dihaloderivative possible in n-pentane are _____.

Answer

To determine the total number of structural dihalo derivatives possible in n-pentane, we will follow a systematic approach.

### Step-by-Step Solution:

1. **Understanding n-Pentane Structure**:
- n-Pentane has a straight-chain structure with five carbon atoms (C1-C5).
- The molecular formula for n-pentane is C5H12.

2. **Identifying Dihalo Derivatives**:
- A dihalo derivative means that two hydrogen atoms in the alkane are replaced by two halogen atoms (X, where X can be F, Cl, Br, or I).
- We need to consider different positions for the halogens on the carbon chain.

3. **Placing Halogens on the Same Carbon**:
- **Case 1**: Both halogens on the same carbon.
- Possible positions: C1, C2, C3, C4, C5.
- This gives us 5 structures:
- C1: X-X-C2-C3-C4
- C2: C1-X-X-C3-C4
- C3: C1-C2-X-X-C4
- C4: C1-C2-C3-X-X
- C5: C1-C2-C3-C4-X-X

4. **Placing Halogens on Different Carbons**:
- **Case 2**: Halogens on different carbons.
- We can have adjacent and non-adjacent placements.
- **Adjacent placements**:
- C1 and C2: X-C1-X-C2-C3-C4
- C2 and C3: C1-X-C2-X-C3-C4
- C3 and C4: C1-C2-X-C3-X-C4
- C4 and C5: C1-C2-C3-X-C4-X
- This gives us 4 structures.
- **Non-adjacent placements**:
- C1 and C3: X-C1-C2-X-C3-C4
- C1 and C4: X-C1-C2-C3-X-C4
- C1 and C5: X-C1-C2-C3-C4-X
- C2 and C4: C1-X-C2-C3-X-C4
- C2 and C5: C1-C2-X-C3-C4-X
- C3 and C5: C1-C2-C3-X-C4-X
- This gives us 6 structures.

5. **Counting All Possible Structures**:
- From Case 1 (same carbon): 5 structures.
- From Case 2 (different carbons): 4 (adjacent) + 6 (non-adjacent) = 10 structures.
- Total = 5 (same) + 10 (different) = 15 structures.

6. **Final Count**:
- The total number of structural dihalo derivatives possible in n-pentane is **15**.

### Final Answer:
The total number of structural dihalo derivatives possible in n-pentane is **15**.