Potassium fluoride

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
Names
IUPAC name
Potassium fluoride
Identifiers
CAS Number
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.029.228
EC Number
  • 232-151-5
PubChem CID
RTECS number
  • TT0700000
UNII
InChI
  • InChI=1S/FH.K/h1H;/q;+1/p-1 Y
    Key: NROKBHXJSPEDAR-UHFFFAOYSA-M Y
  • InChI=1S/FH.K/h1H;/q;+1/p-1
    Key: NROKBHXJSPEDAR-REWHXWOFAI
  • Key: NROKBHXJSPEDAR-UHFFFAOYSA-M
SMILES
  • [F-].[K+]
Properties
Chemical formula
 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)
Solubility in water
 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
Magnetic susceptibility (χ)
 −23.6·10−6 cm3/mol
Structure
Crystal structure
 cubic
Hazards
GHS labelling:
Pictograms
Signal word
 Danger
Hazard statements
 H301, H311, H331[1]
Precautionary statements
 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).
N verify (what is YN ?)
Infobox references

Preparation

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:

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 properties

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

Applications in organic chemistry

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 considerations

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.

References
  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. 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. PMID 33227195. S2CID 227156364.
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