A tosyl group (abbreviated Ts or Tos) is CH₃C₆H₄SO₂. This group is usually derived from the compound tosyl chloride, CH₃C₆H₄SO₂Cl (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.