Sulfonamide: Chemical Structure & Derivatives

Instructor: Korry Barnes

Korry has a Ph.D. in organic chemistry and teaches college chemistry courses.

The primary focal point of this lesson will be on a specific class of organic compounds called sulfonamides. Our topics of discussion will include their structure and some important derivatives.

An Important Class of Drugs

Have you ever had a sinus infection before or perhaps some other type of bacterial infection? Odds are you probably have, and when you go to the doctor usually they prescribe you with some sort of antibiotic to kill the bacteria and help you get better. Have you ever wondered where the antibiotics come from or what's in the pill that actually battles the infection for you? Although there are a LOT of antibiotics out there that are prescribed depending on the circumstances, there is a certain class of organic compounds that is particularly good at combating bacterial organisms.

The class of compounds is known as sulfonamides, and this will be our focal point for this lesson. We will be exploring their structure first, followed by taking a look at some important derivatives that find application in the pharmaceutical industry. Let's get started and find out how important sulfonamides can be!

Structure of Sulfonamides

Let's get started by looking at the structure of sulfonamides. Sulfonamides are composed of a sulfur atom that has two sets of double bonds to two oxygen atoms, a carbon-based side group, and a nitrogen atom bonded to the sulfur itself. In organic chemistry, an amide contains a carbonyl group bonded to a nitrogen atom. Sulfonamides are similar but the carbonyl group is replaced with a sulfone (a sulfur with two oxygen atoms). That's why the term 'amide' appears in the name!

General structure of amides and sulfonamides

The 'R' groups in the figure simply represent any generic carbon-based side chain and could be virtually anything. For example, R could be a methyl group, a benzene ring, an alkane ring, or some other group. If the nitrogen atom contains two hydrogens, the sulfonamide is classified primary, if there is one hydrogen it's secondary, and if no hydrogens are present on the nitrogen, it's a tertiary sulfonamide.

Structures of primary, secondary, and tertiary sulfonamides

Important Sulfonamide Derivatives

As we mentioned earlier, sulfonamides play an extremely important role in the pharmaceutical and drug industries. Let's take a moment and explore some of the more important sulfonamide derivatives.


Sulfanilamide is a synthetic (man-made) sulfonamide that was first prepared in the early 1900's. It is an antibacterial sulfonamide and was actually used by the Allies during World War II to help combat infections brought about by war wounds. Sulfanilamide helped to significantly reduce the mortality rates due to wounds compared to previous wars.

Structure of sulfanilamide, a sulfonamide with antibacterial activity

Although sulfanilamide has been largely replaced with more modern antibiotics especially on the battlefield, it continues to find use in common cases of infections such as yeast infections.


Sulfamethoxazole is another sulfonamide with antibacterial activity and is commonly used in the treatment of urinary tract infections and bronchitis. Sulfamethoxazole looks very similar to sulfanilamide in terms of its structure, but contains an extra ring system called an oxazole.

Structure of sulfamethoxazole, an antibacterial sulfonamide containing an oxazole ring

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