Potassium fluoride

Potassium fluoride
IUPAC name Potassium fluoride
Identifiers
CAS number	(anhydrous) 13455-21-1 (dihydrate) 7789-23-3 (anhydrous) 13455-21-1 (dihydrate) N
PubChem	522689
ChemSpider	23006 Y
UNII	9082WG1G3F Y
EC number	232-151-5
ChEMBL	CHEMBL1644027 N
RTECS number	TT0700000
Jmol-3D images	Image 1
SMILES [F-].[K+]
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
Properties
Molecular formula	KF
Molar mass	58.0967 g/mol (anhydrous) 94.1273 g/mol (dihydrate)
Appearance	white crystals
Density	2.48 g/cm3
Melting point	858 °C (anhydrous) 41 °C (dihydrate) 19.3 °C (trihydrate)
Boiling point	1502 °C
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
Structure
Crystal structure	cubic
Hazards
EU Index	009-005-00-2
EU classification	Toxic (T)
R-phrases	R23/24/25
S-phrases	(S1/2), S26, S45
NFPA 704	0 3 1
Flash point	Non-flammable
LD50	245 mg/kg (oral, guinea pig)
Related compounds
Other anions	Potassium chloride Potassium bromide Potassium iodide
Other cations	Lithium fluoride Sodium fluoride Rubidium fluoride Caesium fluoride
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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. Aqueous solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.

Preparation

Potassium fluoride is prepared by dissolving potassium carbonate in excess 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↑

The salt must not be prepared in glass or porcelain vessels as HF and the aqueous solution of KF corrode glass and porcelain. Heat resistant plastic or platinum containers may be used.

Applications in organic chemistry

In organic chemistry, KF is the preferred source of fluoride for the conversion of chlorocarbons into fluorocarbons.^[1] Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide.^[2]

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. ^ Vogel, A. I.; Leicester, J.; Macey, W. A. T., "n-Hexyl Fluoride", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0525 ; Coll. Vol. 4: 525 
2. ^ 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

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