![]() 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: Precautions cleavage of Si-O bonds in organic synthesis. It will convert electron-deficient aryl chlorides to aryl fluorides ( Halex process), although potassium fluoride is more commonly used.ĭue to the strength of the Si– F bond, fluoride is useful for desilylation reactions, i.e. Similarly to potassium fluoride, CsF reacts with hexafluoroacetone to form a stable perfluoroalkoxide salt. Formation of Cs-F bonds Ĭaesium fluoride serves as a source of fluoride in organofluorine chemistry. CsF gives higher yields in Knoevenagel condensation reactions than KF or NaF. The low nucleophilicity of fluoride means it can be a useful base in organic chemistry. CsF is an alternative to tetra-n-butylammonium fluoride (TBAF) and TAS-fluoride (TASF).Īs with other soluble fluorides, CsF is moderately basic, because HF is a weak acid. ![]() A larger halide ion would allow for the eight-coordination seen in other caesium halide crystals.Īpplications in organic synthesis īeing highly dissociated, CsF is a more reactive source of fluoride than related salts. 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. Structure Ĭaesium 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. ĬsF chains with a thickness as small as one or two atoms can be grown inside carbon nanotubes. CsF reaches a vapor pressure of 1 kilopascal at 825 ☌, 10 kPa at 999 ☌, and 100 kPa at 1249 ☌. It is available in its anhydrous form, and if water has been absorbed, it is easy to dry by heating at 100 ☌ for two hours in vacuo. The reaction is shown below:ĬsF is more soluble than sodium fluoride or potassium fluoride in organic solvents. Using the same reaction, another way to create caesium fluoride is to treat caesium carbonate (Cs 2CO 3) with hydrofluoric acid and again, the resulting salt can then be purified by recrystallization. Ĭaesium 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. Synthesis and properties Crystalline CsF chains grown inside double-wall carbon nanotubes. Caesium also has the highest electropositivity of all known elements and fluorine has the highest electronegativity of all known elements. Caesium fluoride can be used in organic synthesis as a source of the fluoride anion. Caesium fluoride or cesium fluoride is an inorganic compound with the formula CsF and it is a hygroscopic white salt. Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page. One of its compounds, caesium formate, accounts for most of the use of caesium – it’s used as a drilling fluid for oil well drilling. Because francium is below caesium in group 1, it might seem strange that it doesn’t take the title of most reactive metal… but more on that when we get to francium! In the meantime, Periodic Videos have a video showing the reaction of caesium with water.Ĭaesium’s reactivity means that the pure metal doesn’t have a huge number of everyday uses. The group 1 metals increase in reactivity as you descend the group, and caesium is the most reactive of these metals – and the most reactive in the periodic table. Caesium atomic clocks in satellites help GPS and mobile phone networks function. Since 1967, the second has been defined in reference to electron transitions in a caesium-133 atom. Caesium is the element most commonly used in atomic clocks, which provide the most accurate times. ![]()
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