thumb|150px|right|A sulfone. It consists of a sulfonyl group bonded with two organic substituents.
In organosulfur chemistry, a sulfonyl group is either a functional group found primarily in sulfones, or a substituent obtained from a sulfonic acid by the removal of the hydroxyl group, similarly to acyl groups.
Group
Sulfonyl groups can be written as having the general formula , where there are two double bonds between the sulfur and oxygen.
Sulfonyl groups can be reduced to the sulfide with diisobutylaluminium hydride (DIBALH). Lithium aluminium hydride () reduces some but not all sulfones to sulfides.
Examples of sulfonyl group substituents
The names of sulfonyl groups typically end in -syl, such as: