| Fluoroantimonic acid | |||
|---|---|---|---|
| |||
| General | |||
| Systematic name | Fluoroantimonic acid | ||
| Other names | |||
| Molecular formula | HSbF6 | ||
| Acidic power | - 31.3 | ||
| Molar mass | 236.808 g/mole | ||
| Appearance | |||
| CAS number | |||
| Properties | |||
| Density and phase | g cm–3 | ||
| Solubility in water | |||
| Freezing Point | °C at mmHg | ||
| Boiling point | °C at mmHg | ||
| Acidity (pKa) | -25 | ||
| Hazards | |||
| MSDS | |||
| Main hazards | |||
| Flash point | |||
| R/S statement | R: S: | ||
| RTECS number | |||
| Related compounds | |||
| Related acids | HF SbF5 | ||
| Other cations | |||
| Related salts | |||
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |||
Fluoroantimonic acid HFSbF5 is a mixture of hydrogen fluoride and antimony pentafluoride in a various ratios.[1] The 1:1 combination affords one of the strongest known superacids which has been demonstrated to protonate a range of organic compounds to afford carbocations.
The reaction of HF (hydrogen fluoride, not hydrofluoric acid!) and SbF5 is exothermic. HF releases its proton (H+), and its conjugate base (F−) is sequestered by SbF5 forming a strong coordinate bond. The resulting octahedral noncoordinating anion SbF6− is both a very weak nucleophile and a very weak base. The proton effectively becomes "naked", which accounts for the system's extreme acidity. Fluoroantimonic acid is 2×1019 times stronger than 100% sulfuric acid. The autodissociation of fluoroantimonic acid and dissociation back to its constituents can be abbreviated as
File:Fluoroantimonic acid.jpeg
Note, of course, that HSbF6 is rapidly (explosively) decomposed by water. It reacts with virtually all known solvents.[1]
Two related products where crystallised from HF/ SbF5 solutions, and analyzed by X-ray crystallography. These salts consist of either H2F+ and H3F2+ linked to the anion Sb2F11-.[2]
Comparison with other acids
- Fluoroantimonic acid (1990) (H0 Value = −31.3)
- Magic acid (1974) (H0 Value = −19.2)
- Carborane superacid (1969) (H0 Value = −18.0)
- Fluorosulfuric acid (1944) (H0 Value = −15.1)
- Triflic acid (1940) (H0 Value = −14.9)
Note: All values are based upon the Hammett acidity function
References
- ^ a b Olah, G. A.; Prakash, G. K. S.; Wang, Q.; Li, X. “Hydrogen Fluoride–Antimony(V) Fluoride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
- ^ Mootz, D.; Bartmann, K. "The Fluoroniurn Ions H2F+ and H3F2+: Characterization by Crystal Structure Analysis" Angewandte Chemie, International Edition in English 1988, volume 27, pages 391ff.
External links
 | This inorganic compound–related article is a stub. You can help Wikipedia by expanding it. |