Jacobsen reaction

Sulfonation of the aromatic nucleus (method 540) is a reversible reaction. The removal of a sulfonic acid group is important in the preparation of alkylated benzenes by the Jacobsen reaction (method 16). Ortho-disubstituted benzenes are sometimes prepared by using the sulfonic acid group to block the para position. The removal of the sulfonic acid group is usually effected by heating the arylsulfonic acid with aqueous sulfuric acid. 

When polyalkyl- or polyhalobenzenes are treated with sulfuric acid, the ring is sulfonated, but rearrangement also takes place. The reaction, known as the Jacobsen reaction, is limited to benzene rings that have at least four substituents, which can be any combination of alkyl and halogen groups, where the alkyl groups can be... 

Jacobsen reaction 19, 611 Japp-Klingemann cleavage 7,406 19,28,185 Jones reagent (chromium trioxide-sulfuric acid-acetone) 2, 289 12, 335... 

Jacobsen reaction s. 19, 611 Sulfuric acid/irradiation Chlorination... 

The Jacobsen reaction involves the isomerization by sulfuric acid of an aromatic system containing several alkyl halo groups to give vicinal derivatives. 

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