The total 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 to identify all possible isomers.

### Step 1: Understand the structure of n-pentane
n-pentane is a straight-chain alkane with the formula C5H12. Its structure can be represented as:
```
CH3-CH2-CH2-CH2-CH3
```

### Step 2: Identify the positions for the halogens
We need to attach two halogen atoms (let's denote them as X) to the carbon chain. The halogens can be attached to the same carbon or to different carbons.

### Step 3: Count the isomers with both halogens on the same carbon
1. **Both halogens on carbon 1:**
- Structure: X-X-CH2-CH2-CH3
2. **Both halogens on carbon 2:**
- Structure: CH3-X-X-CH2-CH3
3. **Both halogens on carbon 3:**
- Structure: CH3-CH2-X-X-CH3

These give us 3 isomers where both halogens are attached to the same carbon.

### Step 4: Count the isomers with halogens on different carbons
1. **Adjacent carbons (1 and 2):**
- Structure: X-CH2-X-CH2-CH3
- Structure: CH3-X-CH2-X-CH3 (this is the same as above)

2. **Adjacent carbons (2 and 3):**
- Structure: CH3-CH2-X-X-CH3 (this is the same as above)

3. **1 and 3 (leaving one carbon in between):**
- Structure: X-CH2-CH2-X-CH3
- Structure: CH3-X-CH2-CH2-X (this is the same as above)

4. **1 and 4 (leaving two carbons in between):**
- Structure: X-CH2-CH2-CH2-X (this is the same as above)

5. **2 and 4 (leaving one carbon in between):**
- Structure: CH3-X-CH2-CH2-X (this is the same as above)

### Step 5: Count the total isomers
- **From same carbon:** 3 isomers
- **From different carbons:**
- 1 and 2: 1 unique structure
- 2 and 3: 1 unique structure
- 1 and 3: 1 unique structure
- 1 and 4: 1 unique structure
- 2 and 4: 1 unique structure

Adding these up:
- Total from same carbon: 3
- Total from different carbons: 5 (1+1+1+1+1)

### Final Count
Total structural isomers = 3 (same carbon) + 6 (different carbons) = 9

Thus, the total number of structural dihalo derivatives possible in n-pentane is **9**.

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