Which of the following is not a functional group found in penicillin?

• A. Beta-lactam
• B. $\text{Carboxylic acid}\left({\mathrm{CO}}_{2}H\right)$
• C. $\text{Ether}(R-O-R)$
• D. $\text{Amide}(R-{\mathrm{CO}}_{\mathrm{NH}}-R)$

Answer: (C)

Verified step by step guidance

1. Step 1: Understand what a functional group is — a specific group of atoms within molecules that is responsible for the characteristic chemical reactions of those molecules.
2. Step 2: Identify the functional groups present in penicillin by examining its chemical structure. Penicillin contains a beta-lactam ring, which is a four-membered cyclic amide, so it includes both the beta-lactam and amide functional groups.
3. Step 3: Recognize that penicillin also contains a carboxylic acid group (–CO\_2H), which is important for its biological activity and solubility.
4. Step 4: Recall the definition of an ether functional group, which is characterized by an oxygen atom connected to two alkyl or aryl groups (R–O–R). Check if this group appears in the penicillin structure.
5. Step 5: Conclude that since penicillin does not have an ether group (R–O–R) in its structure, ether is the functional group not found in penicillin.