A sulfonanilide group is functional group that is a type of sulfonamide group which contains a sulfur atom bonded to two oxygen, one carbon atom, and one nitrogen contained within a derivative of aniline.
A sulfonanilide group is functional group that is structurally similar to a sulfone group in that contains a sulfur atom bonded to two oxygens. However, instead of the sulfur having two bonds to carbon the sulfur atom is bonded on one side to a nitrogen contained within a derivative of aniline.