Hexafluorophosphoric acid

Structural formula
General
Surname	Hexafluorophosphoric acid
other names	Hexafluorophosphoric acid
Molecular formula	HPF 6
Brief description	colorless liquid
External identifiers / databases
CAS number 16940-81-1 EC number 241-006-5 ECHA InfoCard 100.037.263 PubChem 16211447 Wikidata Q418824
properties
Molar mass	145.97 g mol −1
Physical state	liquid
density	1.77 g cm −3
solubility	miscible with water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 300-310-330-314 P: 310-303 + 361 + 353-304 + 340-301 + 330 + 331-305 + 351 + 338-280
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Hexafluorophosphoric acid is a chemical compound from the group of inorganic acids or phosphorus and fluorine compounds . The commercial product is a 60–70% solution.

Extraction and presentation

Anhydrous hexafluorophosphoric acid can be obtained by reacting hydrogen fluoride with phosphorus pentafluoride , whereby diethyl ether can serve as a solvent:

${\displaystyle \mathrm {PF_{5}+HF\longrightarrow HPF_{6}} }$

It is also possible to use phosphorus pentachloride if heated to 110 ° C:

${\displaystyle \mathrm {PCl_{5}+6HF\longrightarrow HPF_{6}+5\ HCl} }$

Hydrous hexafluorophosphoric acid can also be obtained by reacting phosphoric acid or phosphorus pentoxide with hydrogen fluoride or phosphoric acid with calcium fluoride and sulfuric acid.

${\displaystyle \mathrm {P_{2}O_{5}+12\ HF\longrightarrow 2\ HPF_{6}+5\ H_{2}O} }$

${\displaystyle \mathrm {H_{3}PO_{4}+6\ HF\longrightarrow HPF_{6}+4\ H_{2}O} }$

${\displaystyle \mathrm {H_{3}PO_{4}+3\ CaF_{2}+3\ H_{2}SO_{4}\longrightarrow \ } }$ ${\displaystyle \mathrm {\ HPF_{6}\cdot 4\ H_{2}O+3\ CaSO_{4}} }$

properties

Hexafluorophosphoric acid is only stable in solution. The aqueous solution is colorless, has an acidic reaction ( Brønsted acid ) and can be concentrated up to a concentration of about 75%. Hexafluorophosphoric acid decomposes at elevated temperatures, releasing hydrogen fluoride. The hydrate is called "crystalline hexafluorophosphoric acid". The PF ₆ ^- ions are enclosed by truncated octahedra which, according to earlier assumptions, are formed by water molecules. However, nuclear magnetic resonance spectroscopy and chemical analyzes provide indications that the lattice of the hydrate contains significant amounts of hydrogen fluoride and hydronium ions, even in places that were previously assigned to the water.

use

Hexafluorophosphoric acid is used as a catalyst in photopolymerization .

Many salts of hexafluorophosphoric acid are used for research, e.g. B. the peptide synthesis, or produced for technical applications and sold commercially, as described in more detail in the article Hexafluorophosphate . For example, they are also used in ionic liquids . The most important salt is lithium hexafluorophosphate . This is dissolved in organic solvents with concentrations of 1 mol / l or more and used in lithium ion accumulators , where it supplies the lithium ions for the reactions of the electrodes. At the same time, it ensures very good electrical conductivity and suitable passivation of the aluminum power supply lines used.

Web links

• Preparation of hexafluorophosphoric acid (Freepatentsonline)

Individual evidence

1. ↑ ^{a b c d e f} Entry on hexafluorophosphoric acid in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
2. ↑ Data sheet hexafluorophosphoric acid from AlfaAesar, accessed on April 15, 2010 ( PDF )(JavaScript required) .
3. ↑ George A. Olah , GK Surya Prakash, Arpad Molnar, Jean Sommer: Superacid Chemistry . 2nd Edition. Wiley-Interscience, Hoboken NJ 2009, ISBN 978-0-471-59668-4 , pp.  44 .
4. ↑ ^{a b} Patent DE812247 : Production of hexafluorophosphoric acid and its salts. Registered on March 31, 1949 , published on August 27, 1951 , applicant: Farbenfabriken Bayer, Leverkusen, inventor: Heinz Jonas. ‌
5. ↑ Patent EP 0001394108: Production of hexafluorophosphoric acid
6. ^ DW Davidson, SK Garg: The Hydrate of Hexafluorophosphoric Acid . In: Canadian Journal of Chemistry . tape 50 , no. 21 , November 1, 1972, p. 3515-3520 , doi : 10.1139 / v72-565 .
7. ↑ Jennifer L. Anthony, Edward J. Maginn, Joan F. Brennecke: Solubilities and Thermodynamic Properties of Gases in the Ionic Liquid 1-n-Butyl-3-methylimidazolium Hexafluorophosphate . In: Journal of Physical Chemistry B . tape 106 , no. 29 , July 1, 2002, p. 7315-7320 , doi : 10.1021 / jp020631a .