sulfonic acid definition of sulfonic acid in the Free Online Encyclopedia.

sulfonic acid (səlfŏn`ĭk), organic compound containing the functional group functional group, in organic chemistry, group of atoms within a molecule that is responsible for certain properties of the molecule and reactions in which it takes part.
..... Click the link for more information. RSO₂OH, which consists of a sulfur atom, S, bonded to a carbon atom that may be part of a large aliphatic or aromatic hydrocarbon hydrocarbon (hī'drōkär`bən), any organic compound composed solely of the elements hydrogen and carbon.
..... Click the link for more information. , R, and also bonded to three oxygen atoms, O, one of which has a hydrogen atom, H, attached to it. The hydrogen atom makes the compound acidic, much as the hydrogen of a carboxylic acid (see carboxyl group carboxyl group (kärbŏk`sĭl)
..... Click the link for more information. ) makes it acidic (see acids and bases acids and bases, two related classes of chemicals; the members of each class have a number of common properties when dissolved in a solvent, usually water.

Properties

..... Click the link for more information. ). However, while carboxylic acids are weak (with dissociation constants of about 10⁻⁵), sulfonic acids are considered strong acids (with dissociation constants of about 10⁻²). Because sulfonic acids are so acidic, they generally exist as their salts salt, chemical compound (other than water) formed by a chemical reaction between an acid and a base (see acids and bases ).

Characteristics and Classification of Salts

..... Click the link for more information. and thus tend to be quite soluble in water. Sulfonic acid groups are often introduced into organic molecules such as dyes to stabilize them for use in aqueous dye baths. Sulfonic acid groups also improve the washfastness of wool and silk dyes by enabling the dye to bind more tightly to the fabric. The most important use of sulfonic acid salts (sulfonates) is in the detergent industry. Sodium salts of long-chain aliphatic or aromatic sulfonic acids are used as detergents. Unlike ordinary soaps soap, a cleansing agent. It cleanses by lowering the surface tension of water, by emulsifying grease, and by absorbing dirt into the foam.

Ancient peoples are believed to have employed wood ashes and water for washing and to have relieved the resulting
..... Click the link for more information. , which contain carboxylic acid salts, soaps containing sulfonates do not form a scum in hard water because the calcium and magnesium ions present in the hard water do not form insoluble precipitates with sulfonates as they do with carboxylates. Some sulfonic acid derivatives, e.g., the sulfa drugs, are important as antibiotics.

sulfonic acid [¦səl¦fän·ik ′as·əd]

(organic chemistry)

A compound with the radical ‒SO₂OH, derived by the sulfuric acid replacement of a hydrogen atom; for example, conversion of benzene, C₆H₆, to the water-soluble benzenesulfonic acid, C₆H₅SO₃H, by treatment with sulfuric acid; used to make dyes and drugs.