Which of the following compounds is optically active ?

Options

A. `CH_3CHOHCOOH`
B. `CH_3CH_2COOH`
C. `HOOC CH_2COOH`
D. `CH_3COCOOH`

Answer

To determine which of the given compounds is optically active, we need to identify if any of them contain a chiral carbon. A chiral carbon is defined as a carbon atom that is bonded to four different groups or atoms.

Let's analyze each compound step by step:

### Step 1: Analyze Compound A (CH3-CHOH-COOH)
- The first carbon (CH3) is bonded to three hydrogen atoms, which means it is not chiral.
- The second carbon (CHOH) is bonded to:
- A hydroxyl group (OH)
- A carboxyl group (COOH)
- A methyl group (CH3)
- A hydrogen atom (H)

Since this carbon is bonded to four different groups, it is a chiral carbon. Therefore, Compound A is optically active.

### Step 2: Analyze Compound B (CH3-CH2-COOH)
- The first carbon (CH3) is bonded to three hydrogen atoms, which means it is not chiral.
- The second carbon (CH2) is bonded to:
- Two hydrogen atoms (H)
- A carboxyl group (COOH)

Since this carbon is bonded to two identical hydrogen atoms, it is not chiral. Therefore, Compound B is not optically active.

### Step 3: Analyze Compound C (COOH-CH2-COOH)
- The first carbon (COOH) is bonded to:
- A hydroxyl group (OH)
- Two hydrogen atoms (H)

This carbon is not chiral because it does not have four different groups.
- The second carbon (CH2) is bonded to:
- Two hydrogen atoms (H)
- A carboxyl group (COOH)

This carbon is also not chiral because it has two identical hydrogen atoms. Therefore, Compound C is not optically active.

### Step 4: Analyze Compound D (CH3-COOH)
- The first carbon (CH3) is bonded to three hydrogen atoms, which means it is not chiral.
- The second carbon (COOH) is bonded to:
- A hydroxyl group (OH)
- A carbon atom (C)

This carbon does not have four different groups. Therefore, Compound D is not optically active.

### Conclusion:
The only compound that is optically active is **Compound A (CH3-CHOH-COOH)**, as it contains one chiral carbon.

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