Sulfonamide (chemistry)

In chemistry, the sulfonamide functional group is -S(=O)2-NH2, a sulfone group connected to an amine group.

A sulfonamide (compound) is a compound that contains this group. The general formula is RSO2NH2, where R is some organic group. For example, "methanesulfonamide" is CH3SO2NH2. Any sulfonamide can be considered as derived from a sulfonic acid by replacing a hydroxyl group with an amine group.

In medicine, the term "sulfonamide" is sometimes used as a synonym for sulfa drug, a derivative or variation of sulfanilamide.

Organic synthesis
Sulfonamides can be prepared in the laboratory in many ways:
 * by reaction of sulfonyl chlorides with amines for example in the synthesis of sulfonylmethylamide . A readily available sulfonyl chloride source is tosyl chloride
 * In one study symmetric sulfonamides are prepared directly from amines and sulfur dioxide gas :
 * [[Image:SulfonamideSynthesisfromSO2.png|400px|Sulfonamide synthesis from aniline and sulfur dioxide]]

In this example the reactant is aniline and the catalysts are triethylamine and iodine. Sulfur dioxide is believed to be activated through a series of intermediates: Et3N-I+-I-, Et3N-I+-I3- and Et3N+-SO2-.