Jacobsen rearrangement

The Jacobsen rearrangement is a chemical reaction, commonly described as the migration of an alkyl group in a sulfonic acid derived from a polyalkyl- or polyhalobenzene:

The exact reaction mechanism is not completely clear, but evidence indicates that the rearrangement occurs intermolecularly and that the migrating group is transferred to a polyalkylbenzene, not to the sulfonic acid (sulfonation only takes place after migration). The intermolecular mechanism is partially illustrated by the side products found in the following example:

Furthermore, the reaction is limited to benzene rings with at least four substituents (alkyl and/or halogen groups). The sulfo group is easily removed, so the Jacobsen rearrangement can also be considered as a rearrangement of . It was Herzig who described this type of rearrangement for the first time in 1881 using polyhalogenated benzenesulfonic acids, but the reaction took the name of the German chemist , who described the rearrangement of polyalkylbenzene derivatives in 1886.

References[]

• J. Herzig (1881) "Ueber die Einwirkung von Schwefelsäure auf Mono-, Di- und Tribromobenzol" (On the effect of sulfuric acid on mono-, di- and tribromobenzene), Monatshefte für Chemie, 2 (1) : 192–99. A condensed version of this article appeared in: J. Herzig (1881) "Ueber die Einwirkung von Schwefelsäure auf Mono-, Di- und Tribromobenzol", Berichte der deutschen chemischen Gesellschaft, 14 (1) : 1205–06.
• Oscar Jacobsen (1886) "Ueber die Einwirkung von Schwefelsäure auf Durol und über das dritte Tetramethylbenzol" (On the effect of sulfuric acid on durene [1,2,4,5-tetramethylbenzene] and about the third tetramethylbenzene), Berichte der deutschen chemischen Gesellschaft, 19 : 1209–17.
• L I Smith. Organic Reactions I: The Jacobsen Reaction (Wiley, 1942)
• M B Smith, J March. March's Advanced Organic Chemistry (Wiley, 2001) (ISBN 0-471-58589-0)
• W Pötsch. Lexikon bedeutender Chemiker (VEB Bibliographisches Institut Leipzig, 1989) (ISBN 3817110553)