Fluoroboric acid
- Tetrafluoroboric
- Borofluoric
- Borofluoric
Colorless aqueous solution
Liquid
1.40 g · cm -3
-78 ° C
130 ° C ( decomposition)
Miscible with water
Risk
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Tetrafluoroboric acid is an inorganic acid. Your anion is tetrafluoroborate ( BF4 ). It is commercially available as 45-50 % solution available.
Representation
As large-scale synthesis of tetrafluoroboric acid, the reaction of boric acid with 50 % hydrofluoric acid is used.
A further possibility consists in the reaction of boron trifluoride with hydrofluoric acid.
Properties
Tetrafluoroboric is only stable in solution. The aqueous solution is colorless and can be concentrated to a concentration of about 50 %. Geometrically, the boron atom is tetrahedrally surrounded by four fluorine atoms and forms a spherical anion. The boron atom is sp3 - hybridized in BF4 so. Tetrafluoboric acid has a pKa of 0.4. In aqueous solution, it is dissociated as H3O (aq ) and [ BF4] - (aq ) before.
Use
Tetrafluoroboric acid may be used for the synthesis of fluorinated aromatics. For this purpose, a variant of the Sandmeyer reaction, Diazoaryle be reacted with tetrafluoroboric in a Schiemann reaction.
Further they can be used for removal of the Boc protecting group and a catalyst for polymerization. Tetrafluoroborate ions are weakly coordinating anions. Its salts can therefore easily exchange their anions for more complexing and for this reason often the manufacture of other salts. An example is copper (II) tetrafluoroborate, which is used for the preparation of copper complexes.
Until recent years, the widespread use tetrafluoroboric found as a basis for acidic Zinnelektrolyte. Due to the necessarily resulting amount of fluoride or hydrofluoric acid produced by these electrolytes but a disposal problem. Therefore, electrolytes found today usually based on methanesulfonic acid or sulfuric acid.
Molten alkali metal and Ammoniumtetrafluoroborate (such as sodium, potassium and ammonium tetrafluoroborate ) are good solvents for metal oxides and are used in fluxing agents for soldering and brazing.