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 contains a chiral center, we need to understand what a chiral center is. A chiral center, typically a carbon atom, is one that is bonded to four different groups or atoms.

Let's analyze each option step by step:

### Step 1: Identify the first molecule - 2-chloropropane-2-ol
- **Structure**: This molecule has a three-carbon chain (propane) with a chlorine atom and a hydroxyl group (-OH) attached to the second carbon.
- **Analysis**: The second carbon has two identical carbon groups attached to it (the two -CH3 groups), which means it does not have four different groups. Therefore, **this molecule does not have a chiral center**.

### Step 2: Identify the second molecule - 1-chlorobutane
- **Structure**: This molecule has a four-carbon chain (butane) with a chlorine atom attached to the first carbon.
- **Analysis**: The first carbon has a chlorine atom, a hydrogen atom, and two identical carbon groups (the rest of the butane chain). Since there are two identical groups, **this molecule does not have a chiral center**.

### Step 3: Identify the third molecule - 2-chloropropane
- **Structure**: This molecule has a three-carbon chain with a chlorine atom attached to the second carbon.
- **Analysis**: The second carbon has two identical carbon groups (the two -CH3 groups), which means it does not have four different groups. Therefore, **this molecule does not have a chiral center**.

### Step 4: Identify the fourth molecule - 2-chlorobutane
- **Structure**: This molecule has a four-carbon chain with a chlorine atom attached to the second carbon.
- **Analysis**: The second carbon has four different groups attached:
1. A chlorine atom
2. A hydrogen atom
3. An ethyl group (from the carbon chain)
4. A propyl group (the rest of the butane chain)

Since all four groups are different, **this molecule has a chiral center**.

### Conclusion:
The only molecule that contains a chiral center is **2-chlorobutane**.

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