- Aromatic sulfonation
Aromatic sulfonation is an
organic reactionin which a hydrogen atom on an arene is replaced by a sulfonic acid functional groupin an electrophilic aromatic substitution. Sulfur trioxideis the electrophilein this reaction generated from concentrated sulfuric acid(or fuming sulfuric acid) when heated.
In contrast to
aromatic nitrationand 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.
Aromatic sulfonic acids are intermediates in the preparation of
dyes and many pharmaceuticals. Sulfonation of anilineproduces p-aminobenzenesulfonic acid or sulfanilic acidwhich is a zwitterionwith an unusual high melting point. The amide of this compound and related compounds form a large group of sulfa drugs.
polystyrenecan be used to prepare sodium polystyrene sulfonate.
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