In organosulfur chemistry, a sulfonate is a

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

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 conven ...

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

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 ...

. Its formula is , containing the

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

, where R is typically an

organyl group In organic and organometallic chemistry, an organyl group (commonly denoted by the letter " R") is an organic substituent with one (sometimes more) free valence electron(s) at a carbon atom.. The term is often used in chemical patent literatur ...

, amino group or a

halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...

atom. Sulfonates are the

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

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

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 An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

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 ...

s. A classic preparation of sulfonates is the Strecker sulfite alkylation, in which an

alkali In chemistry, an alkali (; from the Arabic word , ) is a basic 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 soluble base has a pH greater than 7.0. The a ...

sulfite salt displaces a halide, typically in the presence of an

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

catalyst: : An alternative is the condensation of a sulfonyl halide with an alcohol in pyridine: :

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 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), BS3, 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

oxime In organic chemistry, an oxime is an organic compound belonging to the imines, with the general Chemical formula, formula , where R is an organic Side chain, side-chain and R' may be hydrogen, forming an aldoxime, or another organic functional g ...

s 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 (esilate, esylate), * Tosylate (''p''-toluenesulfonate), ''p''- * Benzenesulfonate (besylate), * Closilate (closylate, chlorobenzenesulfonate), * Camphorsulfonate (camsilate, camsylate), * Pipsylate (''p''-iodobenzenesulfonate derivative), ''p''-, where R is any group. * Nosylate (''o''- or ''p''-nitrobenzenesulfonate), ''o''- or ''p''-

References

{{Reflist Functional groups Leaving groups

Sulfonate salts

Sulfonic esters

Sultones

Examples

See also

References