Potassium fluoride

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Potassium fluoride
Potassium-fluoride-3D-ionic.png
Identifiers
CAS number 7789-23-3 YesY, (anhydrous)
13455-21-1 (dihydrate)
PubChem 522689
ChemSpider 23006 YesY
UNII 9082WG1G3F YesY
EC number 232-151-5
ChEMBL CHEMBL1644027 N
RTECS number TT0700000
Jmol-3D images Image 1
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
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 245 mg/kg (oral, rat)[1]
Related compounds
Other anions Potassium chloride
Potassium bromide
Potassium iodide
Other cations Lithium fluoride
Sodium fluoride
Rubidium fluoride
Caesium fluoride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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[edit]

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[edit]

In organic chemistry, KF is the preferred source of fluoride for the conversion of chlorocarbons into fluorocarbons.[2] Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide.[3]

Safety considerations[edit]

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[edit]

  1. ^ http://chem.sis.nlm.nih.gov/chemidplus/rn/7789-23-3
  2. ^ Vogel, A. I.; Leicester, J.; Macey, W. A. T., "n-Hexyl Fluoride", Org. Synth. ; Coll. Vol. 4: 525 
  3. ^ 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