In
organosulfur chemistry
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur ...
, 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 quantitie ...
or
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 ar ...
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
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 rest ...
, 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
![Natriumdodecylbenzolsulfonat](https://upload.wikimedia.org/wikipedia/commons/4/4e/Natriumdodecylbenzolsulfonat.svg)
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 convent ...
s with the general formula are called sulfonates. They 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 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
Scandium trifluoromethanesulfonate, commonly called scandium triflate, is a chemical compound with formula Sc(SO3CF3)3, a salt consisting of scandium cations Sc3+ and triflate anions.
Scandium triflate is used as a reagent in organic chemistr ...
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 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 R
1SO
2OR
2 are called ''sulfonic esters''. Individual members of the category are named analogously to
how ordinary carboxyl esters are named. For example, if the R
2 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 R
1 group is a trifluoromethyl group, the resulting compound is
methyl trifluoromethanesulfonate
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 ...
.
Sulfonic esters are used as reagents in organic synthesis, chiefly because the RSO
3− 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 t ...
, 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, Sulfo-SMCC, etc.
Sultones
![Propio-1,3-sultone](https://upload.wikimedia.org/wikipedia/commons/b/bf/Propio-1%2C3-sultone.svg)
Cyclic sulfonic esters are called sultones. Two examples are
propane-1,3-sultone
1,3-Propane sultone is the organosulfur compound with the formula (CH2)3SO3. It is a cyclic sulfonate ester, a class of compounds called sultones. It is a readily melting colorless solid.
Synthesis
It may be prepared by the acid catalyzed reacti ...
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 a organic compound belonging to the imines, with the general formula , where R is an organic side-chain and R’ may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted ...
s are key intermediates in the synthesis of the anti-convulsant drug
zonisamide
Zonisamide, sold under the brand name Zonegran among others, is a medication used to treat the symptoms of epilepsy and Parkinson's disease. Chemically it is a sulfonamide. It serves as an anticonvulsant used primarily as an adjunctive therapy i ...
.
Tisocromide is an example of a sultone.
Examples
*
Mesylate
In organosulfur chemistry, a mesylate is any salt or ester of methanesulfonic acid (). In salts, the mesylate is present as the anion. When modifying the international nonproprietary name of a pharmaceutical substance containing the group ...
(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 Toluene, tolyl group, –, joined to a sulfonyl group, ––, with the open vale ...
ate (''p''-toluenesulfonate),
*
Benzenesulfonate (besylate),
*
Closilate (closylate, chlorobenzenesulfonate),
*
Camphorsulfonate (camsilate, camsylate),
*
Pipsylate (p-iodobenzenesulfonate derivative).
*
Nosylate
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 on s ...
See also
*
Sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...
*
Sulfoxide
In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl () functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. E ...
*
Sulfonyl
In organosulfur chemistry, a sulfonyl group can refer either to a functional group found primarily in sulfones, or to a substituent obtained from a sulfonic acid by the removal of the hydroxyl group, similarly to acyl groups. Sulfonyl groups c ...
References
{{Reflist
Functional groups
Leaving groups