Fluoroboric acid
Oxonium tetrafluoroborate
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Names | |||
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Preferred IUPAC name
Tetrafluoroboric acid[1] | |||
Other names
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Identifiers | |||
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3D model (
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ChEBI | |||
ChemSpider | |||
ECHA InfoCard
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100.037.165 | ||
EC Number |
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21702 | |||
MeSH | Fluoroboric+acid | ||
PubChem CID
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RTECS number
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UNII | |||
UN number | 1775 | ||
CompTox Dashboard (EPA)
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Properties | |||
H[BF4] | |||
Molar mass | 87.81 g·mol−1 | ||
Appearance | Colourless liquid | ||
Melting point | −90 °C (−130 °F; 183 K) | ||
Boiling point | 130 °C (266 °F; 403 K) | ||
Acidity (pKa) | ~1.8 (MeCN solution)[2] | ||
Hazards | |||
GHS labelling: | |||
Danger | |||
H314 | |||
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501 | |||
NFPA 704 (fire diamond) | |||
Safety data sheet (SDS) | External MSDS | ||
Related compounds | |||
Related compounds
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Fluoroboric acid or tetrafluoroboric acid (archaically, fluoboric acid) is an
It is mainly produced as a precursor to other fluoroborate salts.
Structure and production
Pure H[BF4] has been described as a "nonexistent compound", as a sufficiently "naked" proton is expected to abstract a fluoride from the tetrafluoroborate ion to give hydrogen fluoride and boron trifluoride:
- H+[BF4]− → HF + BF3
The same holds true for the superacids that are known by the simplified formulas
Aqueous solutions of H[BF4] are produced by dissolving boric acid in aqueous hydrofluoric acid.[8][9] Three equivalents of HF react to give the intermediate boron trifluoride and the fourth gives fluoroboric acid:
- B(OH)3 + 4 HF → H3O+ + BF−4 + 2 H2O
Anhydrous solutions can be prepared by treatment of aqueous fluoroboric acid with acetic anhydride.[10]
Acidity
The acidity of fluoroboric acid is complicated by the fact that its name refers to a range of different compounds, e.g. [H(CH3CH2)2O]+[BF4]− (dimethyloxonium tetrafluoroborate), [H3O]+[BF4]− (oxonium tetrafluoroborate), and HF·BF3 (
Applications
Fluoroboric acid is the principal precursor to
Organic chemistry
H[BF4] is used as a
Electroplating
Solutions of H[BF4] are used in the electroplating of tin and tin alloys. In this application, methanesulfonic acid is displacing the use of H[BF4].[11] Fluoroboric acid is also used for high-speed electroplating of copper in fluoroborate baths.[12]
Safety
H[BF4] is toxic and attacks skin and eyes. It attacks glass.[3] It hydrolyzes, releasing corrosive, volatile hydrogen fluoride.[11]
Other fluoroboric acids
A series of fluoroboric acids is known in aqueous solutions. The series can be presented as follows:[13]
- H+[B(OH)4]− (hydrogen tetrahydroxyborate) (not a fluoroboric acid)
- H+[BF(OH)3]− (hydrogen fluoro(trihydroxy)borate)
- H+[BF2(OH)2]− (hydrogen difluoro(dihydroxy)borate)
- H+[BF3(OH)]− (hydrogen trifluoro(hydroxy)borate)
- H+[BF4]− (hydrogen tetrafluoroborate)
See also
References
- . Retrieved 2021-04-08.
- ^
- ^
- PMID 15468064.
- PMID 15791295.
- )
- ISBN 978-3527306732.
- ^ Flood, D. T. (1933). "Fluorobenzene" (PDF). Organic Syntheses. 13: 46; Collected Volumes, vol. 2, p. 295.
- ^ S2CID 91584456.
- ISSN 0026-0576. Retrieved July 21, 2022.
- ISBN 978-0-08-037941-8.
Further reading
- Albert, R.; Dax, K.; Pleschko, R.; Stütz, A. E. (1985). "Tetrafluoroboric acid, an efficient catalyst in carbohydrate protection and deprotection reactions". Carbohydrate Research. 137: 282–290. .
- Bandgar, B. P.; Patil, A. V.; Chavan, O. S. (2006). "Silica supported fluoroboric acid as a novel, efficient and reusable catalyst for the synthesis of 1,5-benzodiazepines under solvent-free conditions". Journal of Molecular Catalysis A: Chemical. 256 (1–2): 99–105. .
- Heintz, R. A.; Smith, J. A.; Szalay, P. S.; Weisgerber, A.; Dunbar, K. R. (2002). Homoleptic Transition Metal Acetonitrile Cations with Tetrafluoroborate or Trifluoromethanesulfonate Anions. Inorganic Syntheses. Vol. 33. pp. 75–83. ISBN 9780471208259.
- Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 307. ISBN 978-0-13-039913-7.
- Meller, A. (1988). "Boron". Gmelin Handbook of Inorganic Chemistry. Vol. 3. New York: Springer-Verlag. pp. 301–310.
- Perry, D. L.; Phillips, S. L. (1995). Handbook of Inorganic Compounds (1st ed.). Boca Raton: CRC Press. p. 1203. ISBN 9780849386718.
- Wamser, C. A. (1948). "Hydrolysis of Fluoboric Acid in Aqueous Solution". Journal of the American Chemical Society. 70 (3): 1209–1215. .
- Wilke-Dörfurt, E.; Balz, G. (1927). "Zur Kenntnis der Borfluorwasserstoffsäure und ihrer Salze". Zeitschrift für Anorganische und Allgemeine Chemie. 159 (1): 197–225. .
External links
- "Fluoroboric Acid ICSC: 1040". INCHEM.