In organosulfur chemistry, a sulfonate is a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

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 k ...

. It contains the

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

, where R is an organic group. Sulfonates are the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

s of sulfonic acids. Sulfonates are generally stable in water, non-

oxidizing Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

, and colorless. Many useful compounds and even some biochemicals feature sulfonates.

Sulfonate salts

Anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s with the general formula are called sulfonates. They are the

s 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 se ...

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 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 w ...

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 flu ...

, typically in the presence of an

iodine Iodine is a chemical element with the Symbol (chemistry), 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 , ...

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 ...

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 In chemistry, a leaving group is defined by the IUPAC as an atom or group of atoms that detaches from the main or residual part of a substrate during a reaction or elementary step of a reaction. However, in common usage, the term is often limited ...

, especially when R is electron-withdrawing.

Methyl triflate Methyl trifluoromethanesulfonate, also commonly called methyl triflate and abbreviated MeOTf, is the organic compound with the formula CF3SO2OCH3. It is a colourless liquid which finds use in organic chemistry as a powerful methylating agent. T ...

, for example, is a strong methylating reagent. Sulfonates are commonly used to confer water solubility to protein crosslinkers such as ''N''-hydroxysulfosuccinimide (Sulfo-NHS),

BS3 BS3 or BS-3 may refer to : * BS3, a BS postcode area for Bristol, England * BS3, a center drill bit size * 100 mm field gun M1944 (BS-3), a 1944 Soviet gun * BisSulfosuccinimidyl suberate, a crosslinker used in biological research * Bežigrad nei ...

, Sulfo-SMCC, etc.

Sultones

Cyclic sulfonic esters are called sultones. Two examples are propane-1,3-sultone and 1,4-butane sultone. 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 In organic chemistry, triflate ( systematic name: trifluoromethanesulfonate), is a functional group with the formula and structure . The triflate group is often represented by , as opposed to −Tf, which is the triflyl group, . For example, ...

(trifluoromethanesulfonate), * Ethanesulfonate (esilate, esylate), *

Tosyl In organic chemistry, a toluenesulfonyl group (tosyl group, abbreviated Ts or Tos) is a univalent functional group with the chemical formula –. It consists of a tolyl group, –, joined to a sulfonyl group, ––, with the open valence o ...

ate (''p''-toluenesulfonate), * Benzenesulfonate (besylate), * Closilate (closylate, chlorobenzenesulfonate), * Camphorsulfonate (camsilate, camsylate), * Pipsylate (p-iodobenzenesulfonate derivative). * Nosylate

References

{{Reflist Functional groups Leaving groups

Sulfonate salts

Sulfonic esters

Sultones

Examples

See also

References