In chemistry, a sulfonamide is an amide of a sulfonic acid, with the general chemical equation R-SO2-NH2, where either of the nitrogenous hydrogen atoms may be replaced by other chemical groups. A large class of antibiotics are based on the sulfonamide structure.
Sulfanilamide was the first clinically useful sulfonamide, no longer used due to toxicity. Gerhard Domagk, who was working on antibacterial, discovered its prototype, Prontosil, in 1935. The French researcher, Daniel Bovet, determined that only the sulfanilamide subunit of Prontosil had antibacterial.
Domagk was awarded a Nobel Prize in 1939, but the Nazi government made him refuse it.