Which of the following is a chiral compound :

Options

A. 2-methyl pentanoic acid
B. 3-methyl pentanoic acid
C. 4-methyl pentanoic acid
D. None of these

Answer

To determine which of the given compounds is chiral, we need to analyze the structure of each compound based on the information provided.

### Step-by-Step Solution:

1. **Understanding Chirality**:
- A molecule is considered chiral if it has a carbon atom that is bonded to four different substituents. This carbon atom is known as a chiral center or stereocenter.

2. **Analyzing 2-Methylpentanoic Acid**:
- The structure of 2-methylpentanoic acid includes a pentanoic acid backbone (5 carbon atoms) with a carboxylic acid group (–COOH) and a methyl group (–CH3) attached to the second carbon.
- The second carbon (the chiral center) has:
- One –COOH group
- One –CH3 group
- One hydrogen atom (H)
- One carbon chain (C) from the rest of the pentanoic acid
- Since all four substituents are different, **2-methylpentanoic acid is chiral**.

3. **Analyzing 3-Methylpentanoic Acid**:
- The structure of 3-methylpentanoic acid also has a pentanoic acid backbone with a methyl group attached to the third carbon.
- The third carbon (the chiral center) has:
- One –COOH group
- One –CH3 group
- One hydrogen atom (H)
- One carbon chain (C) from the rest of the pentanoic acid
- Again, since all four substituents are different, **3-methylpentanoic acid is also chiral**.

4. **Analyzing 4-Methylpentanoic Acid**:
- The structure of 4-methylpentanoic acid has a methyl group on the fourth carbon.
- The fourth carbon (the potential chiral center) has:
- One –COOH group
- Two methyl groups (–CH3) on two sides
- One hydrogen atom (H)
- One carbon chain (C) from the rest of the pentanoic acid
- Here, since two substituents are identical (the two methyl groups), **4-methylpentanoic acid is not chiral**.

5. **Conclusion**:
- The chiral compounds among the given options are **2-methylpentanoic acid and 3-methylpentanoic acid**.

### Final Answer:
The chiral compounds are **2-methylpentanoic acid and 3-methylpentanoic acid**.

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