Caesium fluoride: Difference between revisions

Caesium fluoride
Names
	IUPAC name Caesium fluoride
	Other names Cesium fluoride
Identifiers
CAS Number	13400-13-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	24179 ;
ECHA InfoCard	100.033.156
EC Number	236-487-3;
PubChem CID	25953;
RTECS number	FK9650000;
UNII	T76A371HJR;
CompTox Dashboard (EPA)	DTXSID30893927 ;
	InChI InChI=1S/Cs.FH/h;1H/q+1;/p-1 Key: XJHCXCQVJFPJIK-UHFFFAOYSA-M ; InChI=1/Cs.FH/h;1H/q+1;/p-1 Key: XJHCXCQVJFPJIK-REWHXWOFAY;
	SMILES [F-].[Cs+];
Properties
Chemical formula	CsF
Molar mass	151.903 g/mol
Appearance	white crystalline solid
Density	4.64 g/cm3
Melting point	703 °C (1,297 °F; 976 K)
Boiling point	1,251 °C (2,284 °F; 1,524 K)
Solubility in water	573.0 g/100 mL (25 °C)
Solubility	Insoluble in acetone, diethyl ether, pyridine and ethanol; 191 g/100 mL in methanol.
Magnetic susceptibility (χ)	-44.5·10−6 cm3/mol
Refractive index (nD)	1.477
Structure
Crystal structure	cubic, cF8
Space group	Fm3m, No. 225
Lattice constant	a = 0.6008 nm
Lattice volume (V)	0.2169 nm3
Formula units (Z)	4
Coordination geometry	Octahedral
Dipole moment	7.9 D
Thermochemistry
Heat capacity (C)	51.1 J/mol·K
Std molar; entropy (S⦵298)	92.8 J/mol·K
Std enthalpy of; formation (ΔfH⦵298)	-553.5 kJ/mol
Gibbs free energy (ΔfG⦵)	-525.5 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	toxic
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H315, H318, H331, H361f
Precautionary statements	P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P311, P312, P321, P322, P330, P332+P313, P361, P362, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 0 0
Flash point	Non-flammable
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Caesium chloride; Caesium bromide; Caesium iodide; Caesium astatide
Other cations	Lithium fluoride; Sodium fluoride; Potassium fluoride; Rubidium fluoride; Francium fluoride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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Caesium fluoride or cesium fluoride is an inorganic compound usually encountered as a hygroscopic white solid. It is used in organic synthesis as a source of the fluoride anion. Caesium has the highest electropositivity of all non-radioactive elements and fluorine has the highest electronegativity of all elements.

Synthesis and properties

Crystalline CsF chains grown inside double-wall carbon nanotubes.^[5]

Caesium fluoride can be prepared by the reaction of caesium hydroxide (CsOH) with hydrofluoric acid (HF). The resulting salt can then be purified by recrystallization. The reaction is shown below:

CsOH(aq) + HF(aq) → CsF(aq) + H₂O(l)

Another way to make caesium fluoride is to react caesium carbonate (Cs₂CO₃) with hydrofluoric acid. The resulting salt can then be purified by recrystallization. The reaction is shown below:

Cs₂CO₃(aq) + 2 HF(aq) → 2 CsF(aq) + H₂O(l) + CO₂(g)

In addition, elemental fluorine and caesium can be used to form caesium fluoride as well, but doing so is very impractical because of the expense.^[6] While this is not a normal route of preparation, caesium metal reacts vigorously with all the halogens to form caesium halides. Thus, it burns with fluorine gas, F₂, to form caesium fluoride, CsF according to the following reaction:

2 Cs(s) + F₂(g) → 2 CsF(s)

CsF is more soluble than sodium fluoride or potassium fluoride. It is available in anhydrous form, and if water has been absorbed it is easy to dry by heating at 100 °C for two hours in vacuo.^[7] CsF reaches a vapor pressure of 1 kilopascal at 825 °C, 10 kPa at 999 °C, and 100 kPa at 1249 °C.^[8]

CsF chains with a thickness as small as one or two atoms can be grown inside carbon nanotubes.^[5]

Structure

Caesium fluoride has the halite structure, which means that the Cs⁺ and F⁻ pack in a cubic closest packed array as do Na⁺ and Cl⁻ in sodium chloride.^[3]

Applications in organic synthesis

Being highly dissociated it is a more reactive source of fluoride than related salts. CsF is less hygroscopic alternative to tetra-n-butylammonium fluoride (TBAF) and TAS-fluoride (TASF) when anhydrous "naked" fluoride ion is needed.^{[citation needed]}

As a base

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.^[9] CsF gives higher yields in Knoevenagel condensation reactions than KF or NaF.^[10]

Formation of C-F bonds

Caesium fluoride is also a popular source of fluoride in organofluorine chemistry. For example, CsF reacts with hexafluoroacetone to form a caesium perfluoroalkoxide salt, which is stable up to 60 °C, unlike the corresponding sodium or potassium salt. It will convert electron-deficient aryl chlorides to aryl fluorides (halex reaction).^[11]

Deprotection agent

Due to the strength of the Si–F bond, fluoride ion is useful for desilylation reactions (removal of Si groups) in organic chemistry; caesium fluoride is an excellent source of anhydrous fluoride for such reactions. Removal of silicon groups (desilylation) is a major application for CsF in the laboratory, as its anhydrous nature allows clean formation of water-sensitive intermediates. 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:^[10]

Desilylation is also useful for the removal of silyl protecting groups.^[12]

Other uses

Single crystals of the salt are transparent into the deep infrared. For this reason it is sometimes used as the windows of cells used for infrared spectroscopy.^[13]

Precautions

Like other soluble fluorides, CsF is moderately toxic.^[14] 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.^[15]

References

^ ^a ^b ^c ^d Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.57. ISBN 1-4398-5511-0.
^ Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.132. ISBN 1-4398-5511-0.
^ ^a ^b ^c ^d Davey, Wheeler P. (1923). "Precision Measurements of Crystals of the Alkali Halides". Physical Review. 21 (2): 143. doi:10.1103/PhysRev.21.143.
^ ^a ^b ^c ^d Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 5.10. ISBN 1-4398-5511-0.
^ ^a ^b Senga, Ryosuke; Suenaga, Kazu (2015). "Single-atom electron energy loss spectroscopy of light elements". Nature Communications. 6: 7943. doi:10.1038/ncomms8943. PMC 4532884. PMID 26228378. (Supplementary information)
^ Reacting Fluorine with Caesium. Youtube
^ Friestad, G. K.; Branchaud, B. P. (1999). Reich, H. J.; Rigby, J. H. (eds.). Handbook of Reagents for Organic Synthesis: Acidic and Basic Reagents. New York: Wiley. pp. 99–103. ISBN 978-0-471-97925-8.
^ Lide, D. R., ed. (2005). "Vapor Pressure". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. p. 6.63. ISBN 0-8493-0486-5.
^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–83. ISBN 978-0-08-022057-4.
^ ^a ^b Fiorenza, M; Mordini, A; Papaleo, S; Pastorelli, S; Ricci, A (1985). "Fluoride ion induced reactions of organosilanes: the preparation of mono and dicarbonyl compounds from β-ketosilanes". Tetrahedron Letters. 26 (6): 787–788. doi:10.1016/S0040-4039(00)89137-6.
^ Evans, F. W.; Litt, M. H.; Weidler-Kubanek, A. M.; Avonda, F. P. (1968). "Formation of adducts between fluorinated ketones and metal fluorides". Journal of Organic Chemistry. 33 (5): 1837–1839. doi:10.1021/jo01269a028.
^ Smith, Adam P.; Lamba, Jaydeep J. S.; Fraser, Cassandra L. (2002). "Efficient Synthesis of Halomethyl-2,2'-bipyridines: 4,4'-Bis(chloromethyl)-2,2'-bipyridine". Organic Syntheses. 78: 82; Collected Volumes, vol. 10, p. 107.
^ Reger, Daniel L.; Goode, Scott R.; Ball, David W. (2009-01-27). Chemistry: Principles and Practice. ISBN 978-0534420123.
^ MSDS Listing for cesium fluoride. www.hazard.com. MSDS Date: April 27, 1993. Retrieved on September 7, 2007.
^ "MSDS Listing for cesium chloride." www.jtbaker.com. MSDS Date: January 16, 2006. Retrieved on September 7, 2007.

External links

National Pollutant Inventory-Fluoride and compounds fact sheet

[crc-1] Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.57. ISBN 1-4398-5511-0.

[2] Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.132. ISBN 1-4398-5511-0.

[str-3] Davey, Wheeler P. (1923). "Precision Measurements of Crystals of the Alkali Halides". Physical Review. 21 (2): 143. doi:10.1103/PhysRev.21.143.

[b92t-4] Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 5.10. ISBN 1-4398-5511-0.

[chains-5] Senga, Ryosuke; Suenaga, Kazu (2015). "Single-atom electron energy loss spectroscopy of light elements". Nature Communications. 6: 7943. doi:10.1038/ncomms8943. PMC 4532884. PMID 26228378. (Supplementary information)

[6] Reacting Fluorine with Caesium. Youtube

[Friestad-7] Friestad, G. K.; Branchaud, B. P. (1999). Reich, H. J.; Rigby, J. H. (eds.). Handbook of Reagents for Organic Synthesis: Acidic and Basic Reagents. New York: Wiley. pp. 99–103. ISBN 978-0-471-97925-8.

[8] Lide, D. R., ed. (2005). "Vapor Pressure". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. p. 6.63. ISBN 0-8493-0486-5.

[greenwood-9] Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–83. ISBN 978-0-08-022057-4.

[Fiorenza-10] Fiorenza, M; Mordini, A; Papaleo, S; Pastorelli, S; Ricci, A (1985). "Fluoride ion induced reactions of organosilanes: the preparation of mono and dicarbonyl compounds from β-ketosilanes". Tetrahedron Letters. 26 (6): 787–788. doi:10.1016/S0040-4039(00)89137-6.

[11] Evans, F. W.; Litt, M. H.; Weidler-Kubanek, A. M.; Avonda, F. P. (1968). "Formation of adducts between fluorinated ketones and metal fluorides". Journal of Organic Chemistry. 33 (5): 1837–1839. doi:10.1021/jo01269a028.

[12] Smith, Adam P.; Lamba, Jaydeep J. S.; Fraser, Cassandra L. (2002). "Efficient Synthesis of Halomethyl-2,2'-bipyridines: 4,4'-Bis(chloromethyl)-2,2'-bipyridine". Organic Syntheses. 78: 82; Collected Volumes, vol. 10, p. 107.

[13] Reger, Daniel L.; Goode, Scott R.; Ball, David W. (2009-01-27). Chemistry: Principles and Practice. ISBN 978-0534420123.

[msds-csf-14] MSDS Listing for cesium fluoride. www.hazard.com. MSDS Date: April 27, 1993. Retrieved on September 7, 2007.

[msds-cscl-15] "MSDS Listing for cesium chloride." www.jtbaker.com. MSDS Date: January 16, 2006. Retrieved on September 7, 2007.

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-'''Caesium fluoride''' or '''cesium fluoride''' is an [[inorganic compound]] usually encountered as a [[hygroscopic]] white solid. It is used in [[organic synthesis]] as a source of the fluoride anion.
+'''Caesium fluoride''' or '''cesium fluoride''' is an [[inorganic compound]] usually encountered as a [[hygroscopic]] white solid. It is used in [[organic synthesis]] as a source of the fluoride anion. [[Caesium]] has the highest [[electropositivity]] of all non-radioactive elements and [[fluorine]] has the highest electronegativity of all elements.
 ==Synthesis and properties==