4-Toluenesulfonyl chloride (p-toluenesulfonyl chloride, toluene-p-sulfonyl chloride) is an organic compound with the formula CHCHSOCl.  This white, malodorous solid is a reagent widely used in organic synthesis.  Abbreviated TsCl or TosCl, it is a derivative of toluene and contains a sulfonyl chloride (−SOCl) functional group.