The Jacobsen rearrangement is a

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

, commonly described as the migration of an

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloalk ...

group in a

sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is kn ...

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

substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...

s (alkyl and/or

halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...

groups). The sulfo group is easily removed, so the Jacobsen rearrangement can also be considered as a rearrangement of polyalkylbenzenes. 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

Oscar Jacobsen Oscar Jacobsen (1 January 1850 – 6 August 1902) was a Norwegian engineer and politician for the Liberal Party. Personal life He was born in Vågå as the son of Johanne Georgine Jørgensen and her husband Nils Lauritz Severin Jacobsen. H ...

, 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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

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

on durene ,2,4,5-tetramethylbenzeneand 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) () * W Pötsch. ''Lexikon bedeutender Chemiker'' (VEB Bibliographisches Institut Leipzig, 1989) ({{ISBN, 3817110553) Rearrangement reactions Name reactions