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Properties of Fluoroantimonic Acid

Brief introduction

Name: fluoroantimonic acid

Chemical formula: HSbF6

Relative molecular weight: 236.76

Fluoantimonic acid is a mixture of protonic acid sbf5 and HF, which belongs to super acid. SbF5 can form octahedral anion sbf6 - with fluoride ion. Hydrogen ion can move freely, almost free from binding, so the material has strong acidity, which is 200 billion times of that of pure sulfuric acid. It is the most acidic substance known.

Fluoroantimonic acid, or hexafluoroantimonic acid or hexafluoroantimonic acid, is the product of the reaction of hydrofluoric acid and antimony pentafluoride. When it is mixed in a ratio of one to one, it becomes the strongest known super acid. Experiments show that it can decompose hydrocarbons, produce carbonium ions and hydrogen

Hydrofluoric acid (HF) reacts strongly with antimony pentafluoride (sbf5). HF releases proton H +, and then f − reacts with sbf5 to form octahedral sbf6 − anion. Sbf6 − is a noncoordinate anion with weak nucleophilicity and alkalinity. Therefore, protons are actually "exposed" in water solution, making the mixture system extremely acidic, 2 times stronger than pure sulfuric acid × 10 ^ 19 times


X-ray crystallography was used to study the crystal formed by the reaction of two HF-SbF5 fractions. It was found that the chemical formulas are [h2f] [sb2f11] and [h3f2] [sb2f11], respectively. Both of them contain sb2f11 as anion. It is estimated that the basicity of sb2f11 ion is weaker than that of sbf6, so it is more stable

Comparison with other acids

The following information is based on the Hammett acidity function, which is expressed as a large negative H0 value:

Fluoroantimonic acid (1990) (H0 = − 31.3)

Magic acid (1974) H0 = − 19.2)

Zxq acid (1982) (H0 = − 19.0)

Carboranic acid (1969) (H0 = − 18.0)

Octafluoroplatinum acid (1957) (h0-17.8)

Treble volatile acid (1997) (h0-17.3)

Fluorosulfonic acid (1944) (H0 = − 15.1)

Octafluorochloro (VI) acid (1982) (H0 = -14.9)

Trifluoromethanesulfonic acid (1940) (H0 = − 14.9)

Trifluoro monochloroaluminic acid (1951) (H0 = − 14.7)

Perchloric acid (- 12.9)

Pure sulfuric acid (- 12.0)


Fluoroantimonic acid makes it possible to protonate almost all organic compounds

(CH3)3CH + H → (CH3)3C + H2;

(CH3)4C + H → (CH3)3C + CH4

Fuming fluoroantimonic acid:

Chemical formula: xhsbf6 · ysbf5 · ZHf

Relative molecular weight: indefinite Fuming fluoroantimonic acid is a mixture

Fuming fluoroantimonic acid is a kind of "super acid", which is very similar to magic acid (hso3f. Sbf5 mixture) which was first discovered. It is a kind of corrosive and highly acidic substance. It is said that it can dissolve methane hydrate

CH4 · H2O + HSbF6 = = = CH4 · H3O + (carbocation) + sbf6-

It can also neutralize with methanol to form methyl fluoroantimonate and ionize carbonium ion CH3+

CH3OH+HSbF6====CH3+ +SbF6- +H2O

Therefore, its corrosivity even aims at organic matter. It is said that carbon tetrachloride can be easily dissolved

CCl4+5HSbF6+H2O====CH4·H3O+ +SbF6- +4SbF5+4ClF↑

Fluoroantimonic acid reacts violently with water and sometimes explodes to form water, hydrogen ion and Hexafluoroantimonate ion. At this time, fluoroantimonic acid loses the property of super acid and can no longer make organic matter protonated. However, its strong acidity and strong oxidization still exist. It can corrode some metals (except metal passivation), neutralize some strong bases, dissolve weak bases and alkalinity Amphoteric oxide, can corrode glass.


Fluoroantimonic acid reacts strongly or explosively with water, and it reacts with all known solvents. So2clf, liquid sulfur dioxide and chlorofluorocarbons are the solvents that can dissolve fluoroantimonic acid. The container containing HF-SbF5 can be made of Teflon.


1. Boiling point: none (note that the mixture is fixed without boiling point)

2. Melting point: none (note that the mixture is fixed without melting point)

3. Sbf5 is the solvent, HSbF6 and HF are the solutes. Therefore, both fluoroantimonic acid and fuming fluoroantimonic acid are colorless oily liquids.

4. Oxidation: because it contains pentavalent antimony, so the oxidation is very strong.

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Next:Properties of Fluoroantimony Sulfonic Acid

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