Cesium hydroxide

Crystal structure
__ Cs +      __ OH -
Crystal system	orthorhombic
Space group	Cmcm (No. 63)
Lattice parameters	a  = 4.35  Å , b  = 11.99 Å and c  = 4.516 Å
General
Surname	Cesium hydroxide
Ratio formula	CsOH
Brief description	white to yellow hygroscopic crystals
External identifiers / databases
CAS number 21351-79-1 (anhydrous) 35103-79-8 (monohydrate) EC number 244-344-1 ECHA InfoCard 100.040.298 PubChem 62750 ChemSpider 56494 Wikidata Q296363
properties
Molar mass	149.92 g · mol -1
Physical state	firmly
density	3.68 g cm −3
Melting point	272.3 ° C
solubility	very light in water (3000 g l −1 at 30 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302-314-361f-373 EUH: 071 P: 280-305 + 351 + 338-310
MAK	Switzerland: 2 mg m −3 (measured as inhalable dust )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cesium hydroxide , CsOH, is the hydroxide of cesium . It is one of the strongest bases in aqueous solution .

Extraction and presentation

Cesium hydroxide is formed in addition to hydrogen in the extremely violent reaction (risk of explosion) of water with cesium :

${\displaystyle {\ce {2Cs + 2H2O -> 2CsOH + H2 ^}}}$

Another possibility for synthesis is the reaction of cesium oxide with water.

${\displaystyle {\ce {Cs2O + H2O -> 2CsOH}}}$

Violent reactions can occur during mixing.

Analogous to rubidium hydroxide , cesium hydroxide is also accessible via the sulfate :

${\displaystyle {\ce {Cs2SO4 + Ba(OH)2 -> 2 CsOH + BaSO4}}}$

The resulting barium sulfate precipitates quantitatively and after filtration the cesium hydroxide solution can be carefully concentrated over potassium hydroxide in a platinum dish until the salt separates out. This is then slowly heated to 300 ° C in a silver boat in a stream of dry hydrogen .

properties

Aqueous solutions of cesium hydroxide have a strongly alkaline reaction and etch glass. Cesium hydroxide crystallizes orthorhombically , space group Cmcm (space group no. 63) , with the lattice parameters a  = 4.35  Å , b  = 11.99 Å and c  = 4.516 Å. In the crystal structure, each cesium cation is coordinated by five hydroxide anions, the anions in turn coordinate five cesium ions, resulting in a layered structure. There are also hydrates of cesium hydroxide known. The monohydrate crystallizes tetragonally, space group I 4 ₁ / amd (No. 141) . There are also hexagonal observed forms of the monohydrate. The dihydrate, Cs (OH) · 2 H ₂ O crystallizes orthorhombically , space group Pca 2 ₁ (No. 29) . The trihydrate is monoclinic with the space group P 2 ₁ / n (No. 14, position 2) .

use

Cesium hydroxide is a high-quality base for the catalytic alkynylation of aldehydes and ketones .

Cesium hydroxide is used as an electrolyte in galvanic cells .

Individual evidence

1. ↑ ^{a b c d e} Entry on cesium hydroxide in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
2. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Inorganic Compounds, pp. 4-57.
3. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for cesium hydroxide ), accessed on March 4, 2020.
4. ↑ Georg Brauer: Rubidium and Cesium hydroxide . In: Handbook of Preparative Inorganic Chemistry . Ferdinand Enke Verlag, Stuttgart 1954, p. 742 .
5. ↑ H. Jacobs, B. Harbrecht: A new method of presentation for cesium hydroxide. In: Journal of Nature Research B . 36, 1981, pp. 270-271 ( online ).
6. ↑ R. Černy, V. Favre-Nicolin, B. Bertheville: A tetragonal polymorph of cesium hydroxide monohydrate, CsOH · H ₂ O, from X-ray powder data. In: Acta Crystallographica , C58, 2002, pp. I31-i32, doi : 10.1107 / S0108270101021928 .
7. ↑ ^{a b} D. Mootz, H. Rütter: Hydrates of weak and strong bases. VII: On the cesium hydroxide-water system: The crystal structures of CsOH · 2 H ₂ O and CsOH · 3 H ₂ O. In: Zeitschrift für inorganic und Allgemeine Chemie , 608 (2), 1992, pp 123-130, doi : 10.1002 /zaac.19926080218 .
8. ↑ Entry on cesium compounds. In: Römpp Online . Georg Thieme Verlag, accessed on July 14, 2014.