In organosulfur chemistry, a sulfonate is a salt or ester of a

sulfonic acid In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is kn ...

. It contains the functional group , where R is an organic group. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non- oxidizing, and colorless. Many useful compounds and even some biochemicals feature sulfonates.

Sulfonate salts

Anions with the general formula are called sulfonates. They are the conjugate bases of sulfonic acids with formula . As sulfonic acids tend to be strong

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

s, the corresponding sulfonates are weak bases. Due to the stability of sulfonate anions, the cations of sulfonate salts such as scandium triflate have application as

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

s. A classic

preparation Preparation may refer to: * Preparation (dental), the method by which a tooth is prepared when removing decay and designing a form that will provide adequate retention for a dental restoration * Preparation (music), treatment of dissonance in tona ...

of sulfonates is the Strecker sulfite alkylation, in which an

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...

sulfite Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are wide ...

salt displaces a

halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

, typically in the presence of an

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

catalyst: :RX + M2SO3 -> RSO3M + MX An alternative is the condensation of a sulfonyl halide with an alcohol in pyridine: :ROH + R'SO2Cl\ \overset\ ROSO2R' + HCl

Sulfonic esters

Esters with the general formula R¹SO₂OR² are called ''sulfonic esters''. Individual members of the category are named analogously to how ordinary carboxyl esters are named. For example, if the R² group is a

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

group and the R¹ group is a trifluoromethyl group, the resulting compound is methyl trifluoromethanesulfonate. Sulfonic esters are used as reagents in organic synthesis, chiefly because the RSO₃⁻ group is a good leaving group, especially when R is electron-withdrawing. Methyl triflate, for example, is a strong methylating reagent. Sulfonates are commonly used to confer water solubility to protein crosslinkers such as ''N''-hydroxysulfosuccinimide (Sulfo-NHS),

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, Sulfo-SMCC, etc.

Sultones

Cyclic sulfonic esters are called sultones. Two examples are propane-1,3-sultone and

1,4-butane sultone 1,4-butane sultone is a six-membered δ-sultone and the cyclic ester of 4-hydroxybutanesulfonic acid. As a sulfo-alkylating agent, 1,4-butanesultone is used to introduce the sulfobutyl group (–(CH2)4–SO3−) into hydrophobic compounds posses ...

. Some sultones are short-lived intermediates, used as strong alkylating agents to introduce a negatively charged sulfonate group. In the presence of water, they slowly hydrolyze to the hydroxy sulfonic acids. Sultone oximes are key intermediates in the synthesis of the anti-convulsant drug zonisamide. Tisocromide is an example of a sultone.

Examples

* Mesylate (methanesulfonate), * Triflate (trifluoromethanesulfonate), *

Ethanesulfonate Ethanesulfonic acid (esylic acid) is a sulfonic acid with the chemical formula CH3CH2SO3H. The Conjugate acid, conjugate base is known as ethanesulfonate or, when used in pharmaceutical formulations, as esilate. It is a colorless liquid. Referen ...

(esilate, esylate), * Tosylate (''p''-toluenesulfonate), *

Benzenesulfonate Benzenesulfonic acid (conjugate base benzenesulfonate) is an organosulfur compound with the formula C6 H6 O3 S. It is the simplest aromatic sulfonic acid. It forms white deliquescent sheet crystals or a white waxy solid that is soluble in water ...

(besylate), * Closilate (closylate, chlorobenzenesulfonate), *

Camphorsulfonate Camphorsulfonic acid, sometimes abbreviated CSA or 10-CSA is an organosulfur compound. Like typical sulfonic acids, it is a relatively strong acid that is a colorless solid at room temperature and is soluble in water and a wide variety of organic ...

(camsilate, camsylate), * Pipsylate (p-iodobenzenesulfonate derivative). * Nosylate

References

{{Reflist Functional groups Leaving groups

Sulfonate salts

Sulfonic esters

Sultones

Examples

See also

References