Sulfonated Polystyrene on:
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Typical conditions involve heating the aromatic compound with sulfuric acid:
:
Sulfur trioxide or its protonated derivative is the actual
In the Tyrer sulfonation process (1917), 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 and the benzene fed back to the vessel. In this way an 80% yield is obtained.
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
, aromatic sulfonation is a reaction in which a hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
atom on an arene is replaced by a sulfonic acid () group. Together with nitration and chlorination, aromatic sulfonation is a widely used electrophilic aromatic substitutions. Aryl sulfonic acids are used as detergents, dye, and drug
A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...
s.
:
Stoichiometry and mechanism
Typical conditions involve heating the aromatic compound with sulfuric acid:
:
Sulfur trioxide or its protonated derivative is the actual electrophile
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively Electric charge, charged, have an ...
in this electrophilic aromatic substitution.
To drive the equilibrium, dehydrating agents such as thionyl chloride can be added:
:
Historically, mercurous sulfate has been used to catalyze the reaction.
Chlorosulfuric acid is also an effective agent:
:
In contrast to aromatic nitration and most 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. The reaction is very useful in protecting the aromatic system because of this reversibility. Due to their electron withdrawing effects, sulfonate protecting groups can be used to prevent electrophilic aromatic substitution. They can also be installed as directing groups to affect the position where a substitution may take place.T.W. Graham Solomons: ''Organic Chemistry'', 11th Edition, Wiley, Hoboken, NJ, 2013, p. 676, .
Specialized sulfonation methods
Many method have been developed for introducing sulfonate groups aside from direction sulfonation. A classic named reaction is the Piria reaction ( Raffaele Piria, 1851) in which nitrobenzene is treated with a metal bisulfite forming an aminosulfonic acid as a result of combined nitro group reduction and sulfonation.
In the Tyrer sulfonation process (1917), 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 and the benzene fed back to the vessel. In this way an 80% yield is obtained.
Applications
Aromatic sulfonic acids are intermediates in the preparation of dyes and many pharmaceuticals. Sulfonation of anilines lead to a large group of sulfa drugs. Sulfonation ofpolystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It i ...
is used to make sodium polystyrene sulfonate, a common ion exchange resin
An ion-exchange resin or ion-exchange polymer is a resin or polymer that acts as a medium for ion exchange, that is also known as an ionex. It is an solubility, insoluble matrix (or support structure) normally in the form of small (0.25–1.43&nbs ...
for water softening.
See also
* Electrophilic halogenation * Nitration * PerchlorylbenzeneReferences