Step 1: Identifying the Structure - The given structure consists of an azo (-N=N-) bond and a sulfonamide \((-SO_2NH_2)\) functional group, characteristic of Prontosil. - Prontosil was the first synthetic sulfa drug used as an antibacterial agent.
Step 2: Differentiating Other Compounds - Salvarsan is an arsenic-based antimicrobial drug. - Penicillin is a beta-lactam antibiotic. - Sulphapyridine is another sulfa drug but lacks the azo bond present in Prontosil.
Step 3: Conclusion Since the given structure matches the molecular structure of Prontosil, option (3) is correct.
