Which of the following molecules has a structure most similar to $\mathrm{aspirin}$?

• A. $\mathrm{Phenol}$
• B. $\mathrm{Ibuprofen}$
• C. $\mathrm{Acetaminophen}$
• D. $\mathrm{Methyl} \mathrm{salicylate}$

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the structure of aspirin. Aspirin is also known as acetylsalicylic acid, which contains a benzene ring with two key functional groups: a carboxylic acid (-COOH) and an ester group formed by acetylation of a phenol (-OCOCH3).
2. Step 2: Analyze the structures of the given molecules: Phenol has a benzene ring with a hydroxyl group (-OH); Ibuprofen has a benzene ring with an isobutyl group and a carboxylic acid; Acetaminophen has a benzene ring with a hydroxyl group and an amide group (-NHCOCH3).
3. Step 3: Compare these structures to methyl salicylate, which is an ester formed from salicylic acid (which has a benzene ring with both a hydroxyl and a carboxylic acid group) and methanol. This makes methyl salicylate structurally very similar to aspirin, as both have a benzene ring with ester and hydroxyl/carboxyl functionalities.
4. Step 4: Focus on the functional groups and their positions on the benzene ring. Aspirin and methyl salicylate both have ortho-substituted groups (adjacent positions) on the ring, which is a key structural similarity.
5. Step 5: Conclude that methyl salicylate is the molecule most structurally similar to aspirin because it shares the core aromatic ring and similar functional groups arranged in a comparable manner.