How many enantiomeric pairs are obtained by monochlorination of 2,3-dimethylbutane

Options

A. Nil
B. 4
C. 2
D. 1

Explanation

To determine how many enantiomeric pairs are obtained by the monochlorination of 2,3-dimethylbutane, we can follow these steps:

### Step 1: Understand the structure of 2,3-dimethylbutane
2,3-dimethylbutane is a branched alkane with the following structure:

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

### Step 2: Identify the positions for chlorination
Monochlorination involves the substitution of one hydrogen atom with a chlorine atom. In 2,3-dimethylbutane, chlorination can occur at the following positions:
- At the second carbon (C-2)
- At the third carbon (C-3)

### Step 3: Determine the products of chlorination
1. **Chlorination at C-2**:
- The product will have a chlorine atom at C-2, resulting in:
```
Cl
|
CH3-CH-CH-CH3
|
CH3
```

2. **Chlorination at C-3**:
- The product will have a chlorine atom at C-3, resulting in:
```
CH3
|
CH3-CH-CH-CH3
|
Cl
```

### Step 4: Analyze the chirality of the products
- **Product from chlorination at C-2**:
- This carbon (C-2) becomes chiral because it is bonded to four different groups (Cl, CH3, CH2, and CH3).

- **Product from chlorination at C-3**:
- This carbon (C-3) also becomes chiral for the same reason (Cl, CH3, CH2, and CH3).

### Step 5: Count the number of chiral centers
- Each product has one chiral center:
- Product from C-2 chlorination: 1 chiral center
- Product from C-3 chlorination: 1 chiral center

### Step 6: Determine the number of enantiomeric pairs
- Each chiral center can produce one pair of enantiomers. Therefore, since we have one chiral center from the product of C-2 chlorination and one from C-3 chlorination, we have:
- 1 pair of enantiomers from the C-2 product
- 1 pair of enantiomers from the C-3 product

### Conclusion
Thus, the total number of enantiomeric pairs obtained from the monochlorination of 2,3-dimethylbutane is **1**.

### Final Answer
The number of enantiomeric pairs obtained by monochlorination of 2,3-dimethylbutane is **1**.

---