Organic chemistry

What is the world’s strongest Superacid?

Superacid properties

 World’s strongest Superacid properties and uses?

World's strongest superacid properties and uses

What you need to know about the world’s strongest Superacid fluoroantimonic acid,properties and uses

You may think that the acid in the foreign blood in the popular film is quite wacky, but the truth is, there is an acid that is even more corrosive ! Discover the most powerful superacid of the world: fluoroantimonic acid.


Strongest Superacid

The most powerful superacid in the world is fluoroantimonic acid, HSbF 6 . It is formed by mixing hydrogen fluoride (HF) and antimony pentafluoride (SbF 5 ). Various mixtures produce the superacid, but the mixture of equal ratios of the two acids produces the strongest superacid known to man.

Properties of Superacid Fluoroantimonic Acid

  • Decomposes quickly and explosively on contact with water. Due to this property, fluoroantimonic acid cannot be used in aqueous solution. It is only used in a hydrofluoric acid solution.
  • Evolves highly toxic vapors. When the temperature increases, fluoroantimonic acid decomposes and generates hydrogen fluoride gas (hydrofluoric acid).
  • Fluoroantimonic acid is 2 × 10 19 (20 quintillion) stronger than 100% sulfuric acid . Fluoroantimonic acid has an H 0 value (Hammett acidity function) of -31.3.
  • Dissolves glass and many other materials and protects almost all organic compounds (like everything in your body). This acid is stored in PTFE (polytetrafluoroethylene) containers.

What is World’s strongest Superacid  used  for?

If it’s so toxic and dangerous, why would we want to have fluoroantimonic acid? The answer lies in its extreme properties. Fluoroantimonic acid is used in chemical engineering and organic chemistry to protonate organic compounds, whatever their solvent.

For example, the acid can be used to remove H 2 from isobutane and methane from neopentane. It is used as a catalyst for alkylations and acylations in petrochemicals. Superacids in general are used to synthesize and characterize carbocations.

Reaction between hydrofluoric acid and antimony pentafluoride

The reaction between hydrogen fluoride and antimony pentrafluoride which forms fluoroantimonic acid is exothermic .

HF + SbF 5 → H + SbF 

The hydrogen ion (proton) binds to fluorine via a very weak dipole bond. The weak bond explains the extreme acidity of fluoroantimonic acid, allowing the proton to jump between the clusters of anions.

What makes fluoroantimonic acid a superacid?

A superacid is an acid that is stronger than pure sulfuric acid, H 2 SO 4 . Stronger, this means that a superacid gives more protons or hydrogen ions in water or has an acidity function of Hammet H 0 less than -12. Hammet’s acidity function for fluorantimonic acid is H 0 = -28.

Other superacids

Other superacids include carborane superacids [eg H (CHB 11 Cl 11 )] and fluorosulfuric acid (HFSO 3 ). Carboran superacids can be considered the strongest solo acid in the world, because fluoroantimonic acid is actually a mixture of hydrofluoric acid and antimony pentafluoride. Carborane has a pH of -18. Unlike fluorosulfuric acid and fluoroantimonic acid, carborane acids are so mild that they can be handled with bare skin. Teflon, the non-stick coating often found on cooking utensils, may contain carbon. Carboran acids are also relatively rare, so it is unlikely that a chemistry student will encounter one.

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