n. (context organic chemistry especially in combination English) toluenesulfonyl, phenylmethylsulfonyl
A tosyl group (abbreviated Ts or Tos) is CHCHSO. This group is usually derived from the compound tosyl chloride, CHCHSOCl (abbreviated TsCl), which forms esters and amides of toluenesulfonic or tosylic acid. The para orientation illustrated (p-toluenesulfonyl) is most common, and by convention tosyl refers to the p-toluenesulfonyl group.
Tosylate refers to the anion of p-toluenesulfonic acid (CHCHSO) and it is abbreviated as TsO, or it may refer to esters of p-toluenesulfonic acid.