- Fluoroboric acid
Name = Fluoroboric acid
IUPACName = Tetrafluoroboric acid
OtherNames = Fluoroboric acid; Hydrogen Tetrafluoroborate; Hydrofluoroboric acid; Borofluoric acid
Section1 = Chembox Identifiers
CASNo = 16872-11-0
RTECS = ED2685000
Section2 = Chembox Properties
Formula = HBF4
MolarMass = 87.8126 g/mol
Appearance = Clear liquid
Density = 1.36 g/mL, liquid
3.0 g/L, gas
Solubility = Miscible
MeltingPt = -90 °C
BoilingPt = 130 °C
pKa = -0.4
Section3 = Chembox Structure
CrystalStruct = N/A
Section7 = Chembox Hazards
ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/f2608.htm External MSDS]
MainHazards = Corrosive
FlashPt = nonflammable
RPhrases = 34
SPhrases = 26-36/37/38-45
Section8 = Chembox Related
OtherAnions = Hexafluorophosphoric acid,
OtherCpds = Potassium fluoroborate, nitrosonium fluoroborate,
Hexafluorophosphate, Hydrogen fluoride
Fluoroboric acid is the
chemical compoundwith the formula HBF4. It is the conjugate acid of tetrafluoroborate. It is available commercially as a solution in water and other solvents such as diethyl ether. With a strength comparable to nitric acid, fluoroboric acid is a strong acid with a weakly coordinating, non-oxidizing conjugate base.
Pure fluoroboric acid is unknown. Aqueous solutions of HBF4 can be produced by combining dissolving
boric acidin hydrofluoric acidsolution in aqueous solution at 20-25 °C. [OrgSynth | author = Flood, D. T. | title = Fluorobenzene | collvol = 2 | collvolpages = 295 | prep = CV2P0295] Three equivalents of HF react to give the intermediate boron trifluorideand the fourth gives fluoroboric acid.:: B(OH)3 + 4 HF → H3O+ + BF4- + 2 H2O
Aqueous solutions of fluoroboric acid can also be prepared by treating impure
hexafluorosilicic acidwith solid boric acid followed by removal of precipitated silicon dioxide.Fact|date=September 2007 Anhydrous solutions can be prepared by treatment with acetic anhydride. [Gregory K. Friestad, Bruce P. Branchaud, "Tetrafluoroboric Acid" in "Encyclopedia of Reagents for Organic Synthesis" 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rt035.]
Fluoroboric acid is the principal precursor to
fluoroboratesalts, which are typically prepared by acid-base reactions. The inorganic salts are intermediates in the manufacture of flame-retardant materials, glazing frits, and in electrolytic generation of boron. HBF4 is also used in aluminum etching and acid pickling.
HBF4 is used as a
catalystin for alkylations and polymerizations. In carbohydrate protection reactions, ethereal fluoroboric acid is an efficient and cost-effective catalyst for transacetalation and isopropylidenation reactions. Acetonitrilesolutions cleave acetalsand some ethers, while neatFact|date=September 2007 fluoroboric acid removes tert-butoxycarbonylgroups.
Aqueous HBF4 is used as an
electrolytein galvanic celloxygen sensor systems which consist of an anode, cathode, and oxygen-permeable membrane. The solution of HBF4 is able to dissolve lead(II) oxidefrom the anode in the form of lead tetrafluoroborate while leaving the rest of the system
A mixture of CrO3, HBF4, and
sulfonic acidsin conjunction with a cathode treatment give tin-plated steel. Tin(I) fluoroborate/fluoroboric acid mixtures and organic reagents are used as the electrolyte in the cathode treatment of the tin plating process. Similar processes of electrodepositionand electrolytic stripping are used to obtain specific metal alloys.
Other fluoroboric acids
A series of fluoroboric acids is known in aqueous solutions. The series can be presented as follows [Greenwood&Earnshaw] :
* H [B(OH)4]
* H [BF(OH)3]
* H [BF2(OH)2]
* H [BF3(OH)]
* H [BF4]
* Albert, R.; Dax, K.; Pleschko, R.; Stutz, A. E. "Carbohydr. Res." 1985, "137", 282-290.
* Bandgar, B. P.; Patil, A. V.; Chavan, O.S. "J. Mol. Catal. A: Chem." 2006, "256", 99-105.
* Heintz, R. A.; Smith, J. A.; Szalay, P. S.; Weisgerber, A.; Dunbar, K. R. "Inorg. Synth." 2002, "33", 75.
* Housecroft, C E.; Sharpe, A. G. "Inorganic Chemistry." 2nd ed. New York: Pearson Prentice Hall, 2005. 307.
* Meller, A. "Gmelin Handbook of Inorganic Chemistry: Boron." Vol. 3. New York: Springer-Verlag, 1988. 301-310.
* Perry, D. L.; Phillips, S. L. "Handbook of Inorganic Compounds." Boca Raton: CRC Press, 1995. 1203.
* Wamser, C. A. "J. Am. Chem. Soc." 1948, "70", 1209-1215.
* Wilke-Doerfurt, E.; Balz, G. Z. "Z. Anorg. Allg. Chem." 1927, "159", 224.
* [http://www.inchem.org/documents/icsc/icsc/eics1040.htm INCHEM: Fluoroboric Acid (ICSC)]
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fluoroboric acid — /ˌflʊəroʊbɔrɪk ˈæsəd/ (say .floouhrohbawrik asuhd), /ˌfluroʊ / (say .floohroh ) noun a strong acid, HBF4. Also, hydrofluoboric acid /ˌhaɪdroʊfluəˌbɔrɪkˈæsəd/ (say .huydrohfloohuh.bawrik asuhd), fluoboric acid /ˌfluoʊbɔrɪkˈæsəd/ (say… … Australian English dictionary
fluoroboric acid — noun an acid of fluorine and boron • Hypernyms: ↑acid … Useful english dictionary
fluoroboric acid — noun The acid HBF that is used as a catalyst in organic chemistry See Also: fluoroborate … Wiktionary
Acid — This article is about acids in chemistry. For the drug, see Lysergic acid diethylamide. For other uses, see Acid (disambiguation). Acidity redirects here. For the novelette, see Acidity (Novelette). Acids and Bases … Wikipedia
fluoroboric — adjective Of or pertaining to fluoroboric acid See Also: fluoroborate … Wiktionary
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hydrofluoboric acid — /ˌhaɪdroʊfluəˌbɔrɪk ˈæsəd/ (say .huydrohfloohuh.bawrik asuhd) noun → fluoroboric acid … Australian English dictionary
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