3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||151.903 g/mol|
|Appearance||white crystalline solid|
|Melting point||703 °C (1,297 °F; 976 K) |
|Boiling point||1,251 °C (2,284 °F; 1,524 K)|
|573.0 g/100 mL (25 °C)|
|Solubility||Insoluble in acetone, diethyl ether, pyridine and ethanol|
191 g/100 mL in methanol.
Refractive index (nD)
|Fm3m, No. 225|
a = 0.6008 nm
Lattice volume (V)
Formula units (Z)
Heat capacity (C)
Std enthalpy of
Gibbs free energy (ΔfG˚)
|Safety data sheet||External MSDS|
|GHS Signal word||Danger|
|H301, H311, H315, H318, H331, H361f|
|P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+310, P301+330+331, P302+352, P303+361+353, P304+340, P305+351+338, P308+313, P310, P311, P312, P321, P322, P330, P332+313, P361, P362|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Caesium fluoride or cesium fluoride is an inorganic compound with the formula CsF and it is a hygroscopic white solid. Caesium fluoride can be used in organic synthesis as a source of the fluoride anion. Caesium also has the highest electropositivity of all non-radioactive elements and fluorine has the highest electronegativity of all elements.
Using the same reaction, another way to create caesium fluoride is to treat caesium carbonate (Cs2CO3) with hydrofluoric acid and again, the resulting salt can then be purified by recrystallization. The reaction is shown below:
CsF is more soluble than sodium fluoride or potassium fluoride in organic solvents. It is available in its anhydrous form, and if water has been absorbed, it is easy to dry by heating at 100 °C for two hours in vacuo. CsF reaches a vapor pressure of 1 kilopascal at 825 °C, 10 kPa at 999 °C, and 100 kPa at 1249 °C.
As with other soluble fluorides, CsF is moderately basic, because HF is a weak acid. The low nucleophilicity of fluoride means it can be a useful base in organic chemistry. CsF gives higher yields in Knoevenagel condensation reactions than KF or NaF.
Caesium fluoride serves as a source of fluoride in organofluorine chemistry. Unlike the corresponding sodium or potassium fluorides, CsF reacts with hexafluoroacetone to form a stable perfluoroalkoxide salt. It will convert electron-deficient aryl chlorides to aryl fluorides (Halex process), although potassium fluoride is more commonly used.
Due to the strength of the Si–F bond, fluoride is useful for desilylation reactions, i.e. cleavage of Si-O bonds in organic synthesis. CsF is commonly used for such reactions. Solutions of caesium fluoride in THF or DMF attack a wide variety of organosilicon compounds to produce an organosilicon fluoride and a carbanion, which can then react with electrophiles, for example:
Like other soluble fluorides, CsF is moderately toxic. Contact with acid should be avoided, as this forms highly toxic/corrosive hydrofluoric acid. The caesium ion (Cs+) and caesium chloride are generally not considered toxic.