Fluorosulfuric acid (

IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

name: sulfurofluoridic acid) is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. It is one of the strongest acids commercially available. It is a tetrahedral molecule and is closely related to

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, , substituting a fluorine atom for one of the hydroxyl groups. It is a colourless liquid, although commercial samples are often yellow.Erhardt Tabel, Eberhard Zirngiebl, Joachim Maas "Fluorosulfuric Acid" in "Ullmann's Encyclopedia of Industrial Chemistry" 2005, Wiley-VCH, Weinheim.

Properties

Fluorosulfuric acid is a free-flowing colorless liquid. It is soluble in polar organic solvents (e.g.

nitrobenzene Nitrobenzene is an aromatic nitro compound and the simplest of the nitrobenzenes, with the chemical formula C6H5 NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced ...

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

, and ethyl acetate), but poorly soluble in nonpolar solvents such as alkanes. is one of the strongest known simple Brønsted acids. It has an ''H''₀ value of −15.1 compared to −12 for sulfuric acid. The combination of and the

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 ...

antimony pentafluoride Antimony pentafluoride is the inorganic compound with the formula Sb F5. This colorless, viscous liquid is a strong Lewis acid and a component of the superacid fluoroantimonic acid, formed upon mixing liquid HF with liquid SbF5 in 1:1 ratio. It ...

produces "

Magic acid Magic acid () is a superacid consisting of a mixture, most commonly in a 1:1 molar ratio, of fluorosulfuric acid () and antimony pentafluoride (). This conjugate Brønsted acid, Brønsted–Lewis acid, Lewis superacid system was developed in the 1 ...

", which is a far stronger protonating agent. These acids are categorized as " superacids", acids stronger than 100% sulfuric acid. Reflecting its strong acidity, dissolves almost all organic compounds that are even weak proton acceptors. hydrolyzes slowly to

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

(HF) and

. The related triflic acid () retains the high acidity of but is more hydrolytically stable. The self-ionization of fluorosulfonic acid also occurs: : ''K'' = 4.0 × 10⁻⁸ (at 298 K) isomerizes alkanes and catalyzes the alkylation of hydrocarbons with alkenes, although it is unclear if such applications are of commercial importance. It can also be used as a laboratory fluorinating agent.

Production

Fluorosulfuric acid is prepared by the reaction of HF and sulfur trioxide: : Alternatively, or can be treated with oleum at 250 °C. Once freed from HF by sweeping with an inert gas, HSO₃F can be distilled in a glass apparatus.

Safety

Fluorosulfuric acid is considered to be highly toxic and extremely corrosive. It hydrolyzes to release HF. Addition of water to is similar to, and even more violent than, the addition of water to

References

{{Hydrogen compounds Sulfuryl compounds Fluoro complexes Superacids Mineral acids Fluorinating agents Sulfur oxoacids

Properties

Production

Safety

See also

References