Caesium fluoride

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Caesium fluoride
Caesium fluoride.jpg
Caesium-fluoride-3D-ionic.png
Names
IUPAC name
Caesium fluoride
Other names
Cesium fluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.156 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 236-487-3
PubChem CID
RTECS number
  • FK9650000
UNII
  • InChI=1S/Cs.FH/h;1H/q+1;/p-1 Yes check.svgY
    Key: XJHCXCQVJFPJIK-UHFFFAOYSA-M Yes check.svgY
  • InChI=1/Cs.FH/h;1H/q+1;/p-1
    Key: XJHCXCQVJFPJIK-REWHXWOFAY
  • [F-].[Cs+]
Properties
CsF
Molar mass 151.903 g/mol [1]
Appearancewhite 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]
Std molar
entropy (S⦵298)
92.8 J/mol·K [4]
-553.5 kJ/mol [4]
-525.5 kJ/mol [4]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg
Danger
H301, H311, H315, H318, H331, H361f
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)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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.

Contents

Synthesis and properties

Crystalline CsF chains grown inside double-wall carbon nanotubes. CsF@DWNT.png
Crystalline CsF chains grown inside double-wall carbon nanotubes.

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 perfluoroalkoxide 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]

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]

Related Research Articles

<span class="mw-page-title-main">Caesium</span> Chemical element with atomic number 55 (Cs)

Caesium is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C, which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium has physical and chemical properties similar to those of rubidium and potassium. It is pyrophoric and reacts with water even at −116 °C (−177 °F). It is the least electronegative stable element, with a value of 0.79 on the Pauling scale. It has only one stable isotope, caesium-133. Caesium is mined mostly from pollucite. Caesium-137, a fission product, is extracted from waste produced by nuclear reactors. It has the largest atomic radius of all elements whose radii have been measured or calculated, at about 260 picometres.

<span class="mw-page-title-main">Acyl halide</span> Oxoacid compound with an –OH group replaced by a halogen

In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

<span class="mw-page-title-main">Aluminium chloride</span> Chemical compound

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms a hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.

<span class="mw-page-title-main">Copper(I) chloride</span> Chemical compound

Copper(I) chloride, commonly called cuprous chloride, is the lower chloride of copper, with the formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated hydrochloric acid. Impure samples appear green due to the presence of copper(II) chloride (CuCl2).

<span class="mw-page-title-main">Caesium chloride</span> Chemical compound

Caesium chloride or cesium chloride is the inorganic compound with the formula CsCl. This colorless salt is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chloride ions. Caesium chloride dissolves in water. CsCl changes to NaCl structure on heating. Caesium chloride occurs naturally as impurities in carnallite, sylvite and kainite. Less than 20 tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral pollucite.

<span class="mw-page-title-main">Potassium fluoride</span> Ionic compound (KF)

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 salt and occurs naturally as the rare mineral carobbiite. Solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.

<span class="mw-page-title-main">Bromine trifluoride</span> Chemical compound

Bromine trifluoride is an interhalogen compound with the formula BrF3. At room temperature, it is a straw-coloured liquid with a pungent odor which decomposes violently on contact with water and organic compounds. It is a powerful fluorinating agent and an ionizing inorganic solvent. It is used to produce uranium hexafluoride (UF6) in the processing and reprocessing of nuclear fuel.

<span class="mw-page-title-main">Hafnium tetrachloride</span> Chemical compound

Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst.

Antimony pentafluoride is the inorganic compound with the formula SbF5. This colourless, viscous liquid is a strong Lewis acid and a component of the superacid fluoroantimonic acid, formed upon mixing liquid HF with liquid SbF5 in 1:1 ratio. It is notable for its strong Lewis acidity and the ability to react with almost all known compounds.

<span class="mw-page-title-main">Tetrafluoroborate</span> Anion

Tetrafluoroborate is the anion BF−
4. This tetrahedral species is isoelectronic with tetrafluoroberyllate (BeF2−
4), tetrafluoromethane (CF4), and tetrafluoroammonium (NF+
4) and is valence isoelectronic with many stable and important species including the perchlorate anion, ClO−
4, which is used in similar ways in the laboratory. It arises by the reaction of fluoride salts with the Lewis acid BF3, treatment of tetrafluoroboric acid with base, or by treatment of boric acid with hydrofluoric acid.

<span class="mw-page-title-main">Hexafluorosilicic acid</span> Octahedric silicon compound

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
2SiF
6. Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless.

<span class="mw-page-title-main">Caesium acetate</span> Chemical compound

Caesium acetate or cesium acetate is an ionic caesium compound with the molecular formula CH3COOCs. It is a white solid that may be formed by the reaction of caesium hydroxide or caesium carbonate with acetic acid.

<span class="mw-page-title-main">Caesium chromate</span> Chemical compound

Caesium chromate or cesium chromate is an inorganic compound with the formula Cs2CrO4. It is a yellow crystalline solid that is the caesium salt of chromic acid, and it crystallises in the orthorhombic system.

<span class="mw-page-title-main">Caesium carbonate</span> Chemical compound

Caesium carbonate or cesium carbonate is a chemical compound with the chemical formula Cs2CO3. It is white crystalline solid. Caesium carbonate has a high solubility in polar solvents such as water, ethanol and DMF. Its solubility is higher in organic solvents compared to other carbonates like potassium carbonate and sodium carbonate, although it remains quite insoluble in other organic solvents such as toluene, p-xylene, and chlorobenzene. This compound is used in organic synthesis as a base. It also appears to have applications in energy conversion.

<span class="mw-page-title-main">Thallium(I) chloride</span> Chemical compound

Thallium(I) chloride, also known as thallous chloride, is a chemical compound with the formula TlCl. This colourless salt is an intermediate in the isolation of thallium from its ores. Typically, an acidic solution of thallium(I) sulfate is treated with hydrochloric acid to precipitate insoluble thallium(I) chloride. This solid crystallizes in the caesium chloride motif.

<span class="mw-page-title-main">Caesium bromide</span> Chemical compound

Caesium bromide or cesium bromide is an ionic compound of caesium and bromine with the chemical formula CsBr. It is a white or transparent solid with melting point at 636 °C that readily dissolves in water. Its bulk crystals have the cubic CsCl structure, but the structure changes to the rocksalt type in nanometer-thin film grown on mica, LiF, KBr or NaCl substrates.

<span class="mw-page-title-main">Germanium tetrafluoride</span> Chemical compound

Germanium tetrafluoride (GeF4) is a chemical compound of germanium and fluorine. It is a colorless gas.

<span class="mw-page-title-main">Caesium bicarbonate</span> Chemical compound

Caesium bicarbonate or cesium bicarbonate is a chemical compound with the chemical formula CsHCO3. It can be produced through the following reaction:

<span class="mw-page-title-main">Actinium(III) fluoride</span> Chemical compound

Actinium(III) fluoride (AcF3) is an inorganic compound, a salt of actinium and fluorine.

<span class="mw-page-title-main">Benzyl iodide</span> Chemical compound

Benzyl iodide is an organic compound with the chemical formula C
7H
7I. The compound consists of a benzene ring with an attached iodidemethyl group. The substance is an alkyl halide and is a constitutional isomer of the iodotoluenes.

References

  1. 1 2 3 4 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. ↑ 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. 1 2 3 4 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. 1 2 3 4 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. ↑ 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. ↑ 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. ↑ 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" (PDF). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. p. 6.63. ISBN   0-8493-0486-5.
  9. ↑ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–83. ISBN   978-0-08-022057-4.
  10. 1 2 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. ↑ "MSDS Listing for cesium fluoride". hazard.com. April 27, 1993. Archived from the original on 2012-02-09. Retrieved September 7, 2007.{{cite web}}: CS1 maint: unfit URL (link)
  14. ↑ "MSDS Listing for cesium chloride". hazard.com. JT Baker. January 16, 2006. Archived from the original on 2012-03-13. Retrieved September 7, 2007.{{cite web}}: CS1 maint: unfit URL (link)


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