- Aromatic sulfonation
Aromatic sulfonation is an
organic reaction in which a hydrogen atom on an arene is replaced by asulfonic acid functional group in anelectrophilic aromatic substitution .Sulfur trioxide is theelectrophile in this reaction generated from concentratedsulfuric acid (or fuming sulfuric acid) when heated.In contrast to
aromatic nitration and other electrophilic aromatic substitutions this reaction is reversible. Sulfonation takes place in concentrated acidic conditions and desulfonation is the mode of action in a dilute hot aqueous acid.It is very useful in protecting a piece of an aromatic compound because of this reversibility. See Aromatic Hydration.
Tyrer sulfonation process
In the Tyrer sulfonation process (1917) [US patent|1,210,725] , at some time of technological importance, benzene vapor is led through a vessel containing 90% sulfuric acid the temperature of which is increased from 100 to 180°C. Water and benzene are continuously removed in a condenser and the benzene layer fed back to the vessel. In this way a 80% yield is obtained.
Application
Aromatic sulfonic acids are intermediates in the preparation of
dye s and many pharmaceuticals. Sulfonation ofaniline produces p-aminobenzenesulfonic acid orsulfanilic acid which is azwitterion with an unusual highmelting point . The amide of this compound and related compounds form a large group of sulfa drugs.Sulfonation of
polystyrene can be used to preparesodium polystyrene sulfonate .References
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