text: TsOH is prepared on an industrial scale by the sulfonation of toluene. Common impurities include benzenesulfonic acid and sulfuric acid.  TsOH monohydrate contains an amount of water. To estimate the total moisture present as impurity, the Karl Fischer method is used. Impurities can be removed by recrystallization from its concentrated aqueous solution followed by azeotropic drying with toluene.
  TsOH finds use in organic synthesis as an "organic-soluble" strong acid.  Examples of uses include:
  *Acetalization of an aldehyde.
  *Fischer–Speier esterification
  *Transesterification reactions