Number of chiral centres in Pencillin is

Answer

To determine the number of chiral centers in penicillin, we need to analyze its structure and identify the carbon atoms that are attached to four different substituents. Here’s a step-by-step solution:

### Step 1: Understand the Structure of Penicillin
Penicillin has a characteristic structure that includes a beta-lactam ring, a thiazolidine ring, and various functional groups. The basic structure can be represented as follows:

- A beta-lactam ring (a four-membered cyclic amide)
- A thiazolidine ring (a five-membered ring containing sulfur and nitrogen)
- An R group that varies among different types of penicillin
- A carboxylic acid group (-COOH)

### Step 2: Identify the Carbon Atoms
In the penicillin structure, we need to identify the carbon atoms that could potentially be chiral centers. A chiral center is a carbon atom that is bonded to four different groups.

### Step 3: Analyze Each Carbon Atom
1. **First Carbon**: This carbon is attached to:
- A hydrogen atom
- A nitrogen atom (part of the amide)
- A sulfur atom (part of the thiazolidine ring)
- A carbon atom (part of the beta-lactam ring)
- **Conclusion**: This carbon is a chiral center.

2. **Second Carbon**: This carbon is attached to:
- A hydrogen atom
- A nitrogen atom (part of the amide)
- A carbon atom (part of the thiazolidine ring)
- A carbon atom (part of the beta-lactam ring)
- **Conclusion**: This carbon is also a chiral center.

3. **Third Carbon**: This carbon is attached to:
- A hydrogen atom
- A nitrogen atom (part of the amide)
- A methyl group (-CH3)
- A carboxylic acid group (-COOH)
- **Conclusion**: This carbon is also a chiral center.

### Step 4: Count the Chiral Centers
After analyzing the structure, we find that there are three carbon atoms that meet the criteria for being chiral centers.

### Final Answer
The number of chiral centers in penicillin is **3**.

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