Chlorosulfonation
The chlorosulfonation is an electrophilic aromatic substitution in which a hydrogen on the ring of the aromatics to a sulfonyl chloride group is replaced. It serves to introduce a sulfur function into the aromatic nucleus (Ar). It is usually achieved by reacting the aromatic with chlorosulfonic acid (ArSO 2 Cl). The symmetrical sulfone (ArSO 2 -Ar) is usually formed as a by-product .
General reaction mechanism
When benzene is reacted with chlorosulfonic acid , benzenesulfonyl chloride ( 1 ) is formed, which reacts with sodium hydroxide to form sodium benzenesulfonate ( 2a ), with ammonia to form benzenesulfonamide ( 2b ) or with alcohols to form benzenesulfonic acid ester ( 2c ).
Where Ar describes an aryl radical .
Sulphochlorides are valuable intermediate products in industrial organic chemistry. Through further reactions one arrives at
- Sulphinic acids (ArSO 2 H, reduction with e.g. sulphites, further processing to sulphones (ArSO 2 -R)).
- Thiophenols (ArSH, reduction ),
- Sulfonamides (ArSO 2 NH 2 , aminolysis) or too
- Sulfonic acids (ArSO 3 H, hydrolysis ).
Important follow-up products
- lower alkyl sulfonates (wetting, emulsifying and flotation agents)
- higher alkyl sulfonates (surfactants)
- Acetylsulfanilic acid chloride → sulfonamides
- o -Toluenesulfochloride → saccharin
The sulfo group can be replaced by a hydroxyl group in an alkali melt:
- Phenols
- Naphthols
- alizarin
The starting materials for numerous synthetic dyes are produced from these .
Individual evidence
- ^ Hans Peter Latscha, Uli Kazmaier and Helmut Alfons Klein: Organic Chemistry . Springer, Berlin; Edition: 6th, completely revised edition 2008; ISBN 3-5407-7106-9 ; P. 172.