Caesium fluoride

From Wikipedia, the free encyclopedia

Page Template:Chembox/styles.css has no content.

Template:Chembox IndexlistTemplate:Chembox CompToxTemplate:Chembox OHS (set)Template:Chembox GHS (set)Template:Chembox Datapage check
Caesium fluoride
Lua error in package.lua at line 80: module 'Module:InfoboxImage/data' not found.
Lua error in package.lua at line 80: module 'Module:InfoboxImage/data' not found.
Names
IUPAC name
Caesium fluoride
Other names
Cesium fluoride
Identifiers
Page Template:Plainlist/styles.css has no content.
3D model (JSmol)
 Page Template:Plainlist/styles.css has no content.
ChemSpider Page Template:Plainlist/styles.css has no content.
EC Number Page Template:Plainlist/styles.css has no content.
Page Template:Plainlist/styles.css has no content.
RTECS number Page Template:Plainlist/styles.css has no content.
UNII Page Template:Plainlist/styles.css has no content.
  • InChI=1S/Cs.FH/h;1H/q+1;/p-1 checkY
    Key: XJHCXCQVJFPJIK-UHFFFAOYSA-M checkY
  • InChI=1/Cs.FH/h;1H/q+1;/p-1
    Key: XJHCXCQVJFPJIK-REWHXWOFAY
  • [F-].[Cs+]
Properties
CsF
Molar mass 151.903 g/mol[1]
Appearance white crystalline solid
Density 4.64 g/cm3[1]
Melting point 703 °C (1,297 °F; 976 K)[1]
Boiling point 1,251 °C (2,284 °F; 1,524 K) (2,284 °F; 1,524 K)
573.0 g/100 mL (25 °C)[1]
Solubility Insoluble in acetone, diethyl ether, pyridine and ethanol
191 g/100 mL in methanol.
Basicity (pKb) −744 kJ/mol
−44.5·10−6 cm3/mol[2]
1.477
Structure
cubic, cF8
Fm3m, No. 225[3]
a = 0.6008 nm[3]
0.2169 nm3[3]
4
Octahedral
7.9 D
Thermochemistry
51.1 J/mol·K[4]
92.8 J/mol·K[4]
−553.5 kJ/mol[4]
−525.5 kJ/mol[4]
Hazards
NFPA 704 (fire diamond) Page Template:NFPA 704 diamond/styles.css has no content.

Error: Image is invalid or non-existent.

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).

Template:Chembox Footer/trackingTemplate:Short description

Caesium fluoride (cesium fluoride in American English) is an inorganic compound with the formula CsF. A hygroscopic white salt, caesium fluoride is used in the synthesis of organic compounds as a source of the fluoride anion.[5] The compound is noteworthy from the pedagogical perspective as caesium also has the highest electropositivity of all commonly available elements and fluorine has the highest electronegativity.

Synthesis and properties

File:CsF@DWNT.png
Crystalline CsF chains grown inside double-wall carbon nanotubes.[6]

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

CsOH + HF → CsF + H2O

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:

Cs2CO3 + 2 HF → 2 CsF + H2O + CO2

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.[7] CsF reaches a vapor pressure of 1 kilopascal at 825 °C, 10 kPa at 999 °C, and 100 kPa at 1249 °C.[8]

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] Unlike sodium chloride, caesium fluoride's anion is smaller than its cation, so it is the anion size that sterically inhibits larger coordination numbers than six under normally encountered conditions. A larger halide ion would allow for the eight-coordination seen in other caesium halide crystals.

Applications in organic synthesis

Being highly dissociated, CsF is a more reactive source of fluoride than related alkali metal salts. CsF is an alternative to tetra-n-butylammonium fluoride (TBAF) and TAS-fluoride (TASF).

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 Cs-F bonds

Caesium fluoride serves as a source of fluoride in organofluorine chemistry. Similarly to potassium fluoride, CsF reacts with hexafluoroacetone to form a stable Template:Chem name salt.[11] It will convert electron-deficient aryl chlorides to aryl fluorides (Halex process), although potassium fluoride is more commonly used.

Deprotection agent

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.[12] 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:[10]

File:CsF desilylation.png

Precautions

Like other soluble fluorides, CsF is moderately toxic.[13] 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.[14]

References

Page Template:Reflist/styles.css has no content.

  1. ^ a b c d Page Module:Citation/CS1/styles.css has no content.Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, Florida: CRC Press. p. 4.57. ISBN 1-4398-5511-0.
  2. ^ Page Module:Citation/CS1/styles.css has no content.Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, Florida: CRC Press. p. 4.132. ISBN 1-4398-5511-0.
  3. ^ a b c d Page Module:Citation/CS1/styles.css has no content.Davey, Wheeler P. (1923). "Precision Measurements of Crystals of the Alkali Halides". Physical Review. 21 (2): 143–161. Bibcode:1923PhRv...21..143D. doi:10.1103/PhysRev.21.143.
  4. ^ a b c d Page Module:Citation/CS1/styles.css has no content.Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, Florida: CRC Press. p. 5.10. ISBN 1-4398-5511-0.
  5. ^ Page Module:Citation/CS1/styles.css has no content.Friestad, Gregory K.; Branchaud, Bruce P.; Navarrini, Walter; Sansotera, Maurizio (2007). "Cesium Fluoride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc050.pub2. ISBN 978-0-471-93623-7.
  6. ^ Page Module:Citation/CS1/styles.css has no content.Senga, Ryosuke; Suenaga, Kazu (2015). "Single-atom electron energy loss spectroscopy of light elements". Nature Communications. 6: 7943. Bibcode:2015NatCo...6.7943S. doi:10.1038/ncomms8943. PMC 4532884. PMID 26228378. (Supplementary information)
  7. ^ Page Module:Citation/CS1/styles.css has no content.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. ^ Page Module:Citation/CS1/styles.css has no content.Lide, D. R., ed. (2005). "Vapor Pressure" (PDF). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. p. 6.63. ISBN 0-8493-0486-5.
  9. ^ Page Module:Citation/CS1/styles.css has no content.Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–83. ISBN 978-0-08-022057-4.
  10. ^ a b Page Module:Citation/CS1/styles.css has no content.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. ^ Page Module:Citation/CS1/styles.css has no content.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. ^ Page Module:Citation/CS1/styles.css has no content.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; Page Module:Citation/CS1/styles.css has no content.Collected Volumes, vol. 10, p. 107.
  13. ^ Page Module:Citation/CS1/styles.css has no content."MSDS Listing for cesium fluoride". hazard.com. April 27, 1993. Archived from the original on 2012-02-09. Retrieved September 7, 2007.
  14. ^ Page Module:Citation/CS1/styles.css has no content."MSDS Listing for cesium chloride". hazard.com. JT Baker. January 16, 2006. Archived from the original on 2012-03-13. Retrieved September 7, 2007.


Lua error in package.lua at line 80: module 'Module:Authority control/config' not found. Lua error in package.lua at line 80: module 'Module:Navbox/configuration' not found. Template:Fluorides

Retrieved from "https://cosmopedia.co/index.php?title=Caesium_fluoride&oldid=778520"