the total number of isomeric optically active monochloro derivative of isopentane is

Options

A. two
B. three
C. four
D. one

Explanation

To determine the total number of isomeric optically active monochloro derivatives of isopentane, we can follow these steps:

### Step 1: Understand the structure of isopentane
Isopentane, also known as 2-methylbutane, has the following structure:

```
CH3
|
CH3-CH-CH2-CH3
|
CH2
```

### Step 2: Identify the number of hydrogen atoms
Isopentane has a total of 12 hydrogen atoms (C5H12). When we perform monochlorination, we will replace one of these hydrogen atoms with a chlorine atom (Cl).

### Step 3: Determine possible monochloro derivatives
When chlorinating isopentane, we can replace different hydrogen atoms with chlorine. The positions where chlorine can replace hydrogen are:

1. At the end of the chain (C1)
2. At the second carbon (C2)
3. At the third carbon (C3)
4. At the fourth carbon (C4)

### Step 4: Analyze each position for chirality
- **Chlorination at C1 (end carbon)**:
- Structure: CH3-CH(CH2Cl)-CH2-CH3
- No chiral center (two identical hydrogen atoms).

- **Chlorination at C2 (second carbon)**:
- Structure: CH3-CH(Cl)-CH2-CH3
- This carbon has four different substituents (CH3, CH2, H, Cl), so it is a chiral center. This gives us one optically active isomer.

- **Chlorination at C3 (third carbon)**:
- Structure: CH3-CH2-CH(Cl)-CH3
- This carbon also has four different substituents (CH3, CH2, H, Cl), making it another chiral center. This gives us another optically active isomer.

- **Chlorination at C4 (end carbon)**:
- Structure: CH3-CH2-CH2-CH(Cl)
- No chiral center (two identical hydrogen atoms).

### Step 5: Count the optically active isomers
From the analysis:
- C1 and C4 do not contribute to optically active isomers.
- C2 contributes 1 optically active isomer.
- C3 contributes 1 optically active isomer.

Thus, the total number of isomeric optically active monochloro derivatives of isopentane is **2**.

### Final Answer:
The total number of isomeric optically active monochloro derivatives of isopentane is **2**.

---