A sulfonyl group's an organic radical or functional group obtained from a sulfonic acid by the removal of the hydroxyl group. Sulfonyl groups can be written as having the general formula R-S(=O)2-R', where there're two double bonds between the sulfur and oxygen. The names of sulfonyl groups typically end in -syl, such as in tosyl chloride which's p-toluenesulfonyl chloride, CH3C6H4SO2Cl or mesyl chloride which's methylsulfonyl chloride, CH3SO2Cl. Sulfonyl groups can be reduced to the hydrocarbon… (More on Sulfonyl)