Sulfonic acid 1615402 213791171 2008-05-20T21:02:15Z Johner 1173323 /* Sulfonic acids */ [[Image:Sulfonic acid chemical structure.png|thumb|98px|Chemical structure of sulfonic acid.]] '''Sulfonic acid''' is an unstable [[acid]] with the formula H-S(=O)<sub>2</sub>-OH. Sulfonic acid is the less stable [[tautomer]] of [[sulfurous acid]] HO-S(=O)-OH into which sulfonic acid converts rapidly. Derived compounds which replace the sulfur-bonded hydrogen with organic groups are stable. These may then form [[salt]]s or [[ester]]s, called [[sulfonate]]s. == Sulfonic acids== [[Image:Methanesulfonic-acid-3D-balls.png|thumb|right|200px|[[Ball-and-stick model]] of methanesulfonic acid]] '''Sulfonic acids''' are a class of [[organic acid]]s with the general formula ''R''-S(=O)<sub>2</sub>-OH, where ''R'' is usually a [[hydrocarbon]] [[side chain]]. Sulfonic acids are typically much stronger acids than their [[carboxyl|carboxylic]] equivalents, and have the unique tendency to bind to [[protein]]s and [[carbohydrate]]s tightly; most "washable" [[dye]]s are sulfonic acids (or have the functional [[sulfonyl]] group in them) for this reason. They are also used as [[catalyst]]s and intermediates for a number of different products. Sulfonic acids and their salts ([[sulfonate]]s) are used extensively in such diverse products like [[detergents]], antibacterial drugs [[Sulfonamide (medicine)|sulfa drug]]s, anion exchange resins (water purification) and dyes. The simplest example is [[methanesulfonic acid]], CH<sub>3</sub>SO<sub>2</sub>OH, which is a [[reagent]] regularly used in [[organic chemistry]]. [[P-Toluenesulfonic acid|''p''-Toluenesulfonic acid]] is also an important reagent. == Sulfonic acid chlorides == '''Sulfonic acid chlorides''' are a class of [[organic compound]]s with the general formula R-SO<sub>2</sub>-Cl. These compounds react readily with nucleophiles (like [[alcohol]]s, [[amine]]s etc.) If the nucleophile is an alcohol the product is a sulfonic ester, if it is an amine the product is a sulfonamide. Important sulfonic acid chlorides are [[tosyl]] chloride, [[brosylate|brosyl]] chloride, [[nosylate|nosyl]] chloride and [[mesylate|mesyl]] chloride. One synthetic procedure to synthesize sulfonic acid chlorides is the [[Reed reaction]]. Sulfonyl chloride is very prone to hydrolysis. An ice/water bath can be used to decrease this effect (Titus 1982 & Lefevre 1996). == Sulfonic esters == [[Image:Methyl triflate.png|thumb|right|Methyl triflate]] '''Sulfonic esters''' are a class of [[organic compound]]s with the general formula R-SO<sub>2</sub>-OR. Sulfonic esters such as [[methyl triflate]] are considered good [[leaving group]]s in [[nucleophilic aliphatic substitution]]. == See also == * [[Sulfuric acid]] H<sub>2</sub>SO<sub>4</sub> * [[Sulfonium]] S<sup>+</sup>, S<sup>+</sup>R<sub>3</sub> ==References== * J.A. Titus, R. Haugland, S.O. Sharrow and D.M. Segal , Texas red, a hydrophilic, red-emitting fluorophore for use with fluorescein in dual parameter flow microfluorometric and fluorescence microscopic studies. J. Immunol. Methods 50 (1982), pp. 193–204. {{DOI|10.1016/0022-1759(82)90225-3}} * C. Lefevre, H.C. Kang, R.P. Haugland, N. Malekzadeh, S. Arttamangkul, and R. P. Haugland, Texas Red-X and Rhodamine Red-X, New Derivatives of Sulforhodamine 101 and Lissamine Rhodamine B with Improved Labeling and Fluorescence Properties, Bioconj Chem 1996, 7(4):482-9 {{doi|10.1021/bc960034p}} {{Functional Groups}} [[Category:Sulfonic acids| ]] [[Category:Functional groups]] [[da:Sulfonat]] [[de:Sulfonsäuren und Sulfonate]] [[es:Ácido sulfónico]] [[fr:Acide sulfonique]] [[it:Acidi solfonici]] [[nl:Sulfonzuur]] [[ja:スルホン酸]] [[pt:Ácido sulfônico]] [[ru:Сульфокислоты]] [[sk:Sulfonácia]] [[zh:磺酸]]