Sulfonation

sulfonation [‚səl·fə′nā·shən]

(chemistry)

Substitution of ‒SO₃H groups (from sulfuric acid) for hydrogen atoms, for example, conversion of benzene, C₆H₆, into benzenesulfonic acid, C₆H₅SO₃H.

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Sulfonation 

the substitution of a sulfo group (—SO₃H) for a hydrogen atom attached to a carbon atom in an organic compound under the action of sulfuric acid or oleum. Sulfonation of aromatic compounds is most common—for example,

C₆H₆ + H₂SO₄ → C₆H₅SO₃H + H₂O

In the case of aliphatic compounds, the sulfo group is usually introduced indirectly, for example, by the exchange of a halogen atom in halide derivatives (1) or by the action of sulfur dioxide and chlorine on hydrocarbons upon irradiation with ultraviolet light (sulfochlorination), with subsequent hydrolysis (2):

(1) CH₂═CH—CH₂Cl + NaHSO₃ → CH₂═CH—CH₂SO₃H + NaCl

(In these formulas R represents a hydrocarbon radical—for example, an alkyl.)

Compounds that are not resistant to acids are sulfonated by sulfur trioxide bound in a complex—for example, in sulfur trioxide-dioxane:

Sulfonation and sulfochlorination are important industrial processes that are widely used in the production of sulfonic acids and ion-exchange resins.

B. L. DIATKIN