In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the of sulfonic acids. Sulfonates are generally stable in water, non-oxidizing, and colorless. Many useful compounds and even some biochemicals feature sulfonates.
Sulfonate salts
with the general formula are called sulfonates. They are the
of sulfonic acids with formula . As sulfonic acids tend to be strong
, 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
.
A classic organic reaction of sulfonates is the Strecker sulfite alkylation, in which an alkali sulfite salt displaces a halide, typically in the presence of an iodine catalyst:
An alternative is the condensation of a sulfonyl halide with an alcohol in pyridine:
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 group and the R
1 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.
[R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996) ] 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
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),
-
( 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-
See also
