Jacobsen Rearrangement

Abstract The polysubstituted aromatics conversion into corresponding sulfonated aromatics with the migration of substituents in contact with concentrated sulfuric acid and under these conditions, the halogenated polyalkylaromatics undergo disproportionation of halogen atoms. Hence, this reaction is generally referred to as the Jacobsen rearrangement or Jacobsen reaction. In addition, the study finds that among the polyalkyl benzenes, only the tetraalkyl or pentaalkyl benzenes undergo this reaction. On the other hand, hexaalkyl benzenes, are more stable toward concentrated sulfuric acid, even if they are in contact with it for several months. This reaction is always followed by the evolution of sulfur dioxide, together with the production of amorphous tarry byproducts. More over, this rearrangement is worked for polyalkyl as well as halogenated aromatics and the fluorinated aromatics are the exceptions. For the case of halogenated aromatic compounds, halogen atoms often migrate to give disproportionated products. This reaction has been used to prepare multisubstituted alkyl aromatics with substituents in the vicinal position.