Desulfonation reaction

See also: Aromatic sulfonation

In organic chemistry, the desulfonation reaction is the hydrolysis of aryl and naphthyl sulfonic acids:^[1]

RC₆H₄SO₃H + H₂O → RC₆H₅ + H₂SO₄

It is the reverse of sulfonation.^[2] The temperature of desulfonation correlates with the ease of the sulfonation.

Applications in synthesis

This reactivity is exploited in the regiospecific preparation of many di- and tri-substituted aromatic compounds. The approach exploits the meta-directing effect of the sulfonic acid group. 2-Chlorotoluene for example can be prepared by chlorination of p-toluenesulfonic acid, followed by hydrolysis. The method is also useful for the preparation of 2,6-dinitroaniline^[3] and 2-bromophenol via phenol-2,4-disulfonic acid.^[4]