Potassium fluoride

Summary

Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare mineral carobbiite. Solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.

Potassium fluoride
Potassium-fluoride-3D-ionic.png
Names
IUPAC name
Potassium fluoride
Identifiers
  • 7789-23-3 (anhydrous) checkY
  • 13455-21-5 (dihydrate) checkY
3D model (JSmol)
  • Interactive image
ChEMBL
  • ChEMBL1644027 ☒N
ChemSpider
  • 23006 checkY
ECHA InfoCard 100.029.228 Edit this at Wikidata
EC Number
  • 232-151-5
  • 522689
RTECS number
  • TT0700000
UNII
  • 9082WG1G3F checkY
  • 95R1D12HEH (dihydrate) checkY
  • DTXSID8031940 Edit this at Wikidata
  • InChI=1S/FH.K/h1H;/q;+1/p-1 checkY
    Key: NROKBHXJSPEDAR-UHFFFAOYSA-M checkY
  • InChI=1S/FH.K/h1H;/q;+1/p-1
    Key: NROKBHXJSPEDAR-REWHXWOFAI
  • Key: NROKBHXJSPEDAR-UHFFFAOYSA-M
  • [F-].[K+]
Properties
KF
Molar mass 58.0967 g/mol (anhydrous)
94.1273 g/mol (dihydrate)
Appearance colourless
Density 2.48 g/cm3
Melting point 858 °C (1,576 °F; 1,131 K) (anhydrous)
41 °C (dihydrate)
19.3 °C (trihydrate)
Boiling point 1,502 °C (2,736 °F; 1,775 K)
anhydrous:
92 g/100 mL (18 °C)
102 g/100 mL (25 °C)
dihydrate:
349.3 g/100 mL (18 °C)
Solubility soluble in HF
insoluble in alcohol
−23.6·10−6 cm3/mol
Structure
cubic
Hazards
GHS labelling:
GHS06: Toxic
Danger
H301, H311, H331[1]
P261, P264, P270, P271, P280, P301+P310, P302+P352, P304+P340, P311, P312, P321, P322, P330, P361, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
245 mg/kg (oral, rat)[2]
Related compounds
Other anions
Potassium chloride
Potassium bromide
Potassium iodide
Other cations
Lithium fluoride
Sodium fluoride
Rubidium fluoride
Caesium fluoride
Francium fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

PreparationEdit

Potassium fluoride is prepared by dissolving potassium carbonate in hydrofluoric acid. Evaporation of the solution forms crystals of potassium bifluoride. The bifluoride on heating yields potassium fluoride:

K2CO3 + 4HF → 2KHF2 + CO2↑ + H2O
KHF2 → KF + HF↑

Platinum or heat resistant plastic containers are often used for these operations.

Potassium chloride converts to KF upon treatment with hydrogen fluoride. In this way, potassium fluoride is recyclable.[3]

Crystalline propertiesEdit

KF crystallizes in the cubic NaCl crystal structure. The lattice parameter at room temperature is 0.266 nm.[4]

Applications in organic chemistryEdit

In organic chemistry, KF can be used for the conversion of chlorocarbons into fluorocarbons, via the Finkelstein (alkyl halides)[5] and Halex reactions (aryl chlorides).[3] Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide.[6] More efficient fluorination of aliphatic halides can be achieved with a combination of crown ether and bulky diols in acetonitrile solvent.[7]

Safety considerationsEdit

Like other sources of the fluoride ion, F, KF is poisonous, although lethal doses approach gram levels for humans. It is harmful by inhalation and ingestion. It is highly corrosive, and skin contact may cause severe burns.

ReferencesEdit

  1. ^ "Potassium Fluoride". sigmaaldrich.com. Retrieved 2018-12-20.
  2. ^ Chambers, Michael. "ChemIDplus - 7789-23-3 - NROKBHXJSPEDAR-UHFFFAOYSA-M - Potassium fluoride - Similar structures search, synonyms, formulas, resource links, and other chemical information". chem.sis.nlm.nih.gov.
  3. ^ a b Siegemund, Günter; Schwertfeger, Werner; Feiring, Andrew; Smart, Bruce; Behr, Fred; Vogel, Herward; McKusick, Blaine (2002). "Fluorine Compounds, Organic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a11_349..
  4. ^ "Potassium fluoride". University College London.
  5. ^ Vogel, A. I.; Leicester, J.; Macey, W. A. T. (1956). "n-Hexyl Fluoride". Organic Syntheses. 36: 40. doi:10.15227/orgsyn.036.0040.
  6. ^ Han, Q.; Li, H-Y. "Potassium Fluoride" in Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons,New York. doi:10.1002/047084289X.rp214
  7. ^ Silva, Samuel L.; Valle, Marcelo S.; Pliego, Josefredo R. (2020-12-04). "Nucleophilic Fluorination with KF Catalyzed by 18-Crown-6 and Bulky Diols: A Theoretical and Experimental Study". The Journal of Organic Chemistry. 85 (23): 15457–15465. doi:10.1021/acs.joc.0c02229. ISSN 0022-3263.