Which of the following molecules contain a chiral centre?

Options

A. 2-chloropropan-2-ol
B. 1-chlorobutane
C. 2-chloropropane
D. 2-chlorobutane

Answer

To determine which of the given molecules contain a chiral center, we need to analyze each molecule's structure and identify if there is a carbon atom bonded to four different groups. A chiral center is typically a carbon atom that has four different substituents attached to it.

### Step-by-Step Solution:

1. **Identify the Molecules**: We will analyze the following molecules:
- 2-chloro-propane-2-ol
- 1-chloro-butane
- 2-chloro-propane
- 2-chloro-butane

2. **Analyze 2-chloro-propane-2-ol**:
- Structure: The carbon at position 2 is attached to:
- OH group
- Two methyl groups (CH₃)
- One hydrogen atom (H)
- Since two of the substituents are identical (the two methyl groups), this carbon does not have four different groups. Therefore, **2-chloro-propane-2-ol does not have a chiral center**.

3. **Analyze 1-chloro-butane**:
- Structure: The carbon at position 1 is attached to:
- Chlorine (Cl)
- Three hydrogen atoms (H)
- Since three of the substituents are identical (the three hydrogens), this carbon does not have four different groups. Therefore, **1-chloro-butane does not have a chiral center**.

4. **Analyze 2-chloro-propane**:
- Structure: The carbon at position 2 is attached to:
- Chlorine (Cl)
- Two methyl groups (CH₃)
- One hydrogen atom (H)
- Again, since two of the substituents are identical (the two methyl groups), this carbon does not have four different groups. Therefore, **2-chloro-propane does not have a chiral center**.

5. **Analyze 2-chloro-butane**:
- Structure: The carbon at position 2 is attached to:
- Chlorine (Cl)
- Methyl group (CH₃)
- Hydrogen atom (H)
- Ethyl group (C₂H₅)
- All four substituents are different (Cl, CH₃, H, and C₂H₅). Therefore, **2-chloro-butane has a chiral center**.

### Conclusion:
The molecule that contains a chiral center is **2-chloro-butane**.