Cesium carbonate

Structural formula
General
Surname	Cesium carbonate
Molecular formula	Cs 2 CO 3
Brief description	white odorless solid
External identifiers / databases
CAS number 534-17-8 EC number 208-591-9 ECHA InfoCard 100.007.812 PubChem 10796 ChemSpider 10339 Wikidata Q416923
properties
Molar mass	325.82 g mol −1
Physical state	firmly
density	4.07 g cm −3
Melting point	610 ° C
solubility	good in water (2615 g l −1 at 15 ° C) good in ethanol
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
Toxicological data	2333 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−1139.7 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cesium carbonate is a chemical compound of cesium and is one of the carbonates . It is mainly used as a base in organic synthesis .

Extraction and presentation

Cesium carbonate can be obtained from pollucite / spodumene concentrates. For this purpose, this z. B. heated under pressure with a calcium hydroxide solution to 220 ° C ( hydrothermal ). After filtration of insoluble calcium silicates, precipitation of excess calcium as well as lithium salts present in the mineral with carbon dioxide as carbonate, an alkaline cesium carbonate solution remains. This can then z. B. be neutralized with sulfuric acid . A cesium-aluminum-alum is formed, which is further purified by recrystallization . Cesium hydroxide is then produced from this salt, which is ultimately converted into the purest cesium carbonate by means of carbon dioxide.

properties

Cesium carbonate is hygroscopic and easily dissolves in water. Aqueous cesium carbonate solutions have a basic reaction in the same way as other alkali carbonates. In contrast to the other alkali carbonates except the expensive rubidium carbonate , cesium carbonate is also soluble in many organic solvents. Cesium carbonate crystallizes in the monoclinic crystal system in the space group P 2 ₁ / c (space group no. 14) and with the lattice parameters a = 612.64 pm, b = 1027.65 pm, c = 814.76 pm, β = 95.85 ° as well as four formula units per unit cell . It dissociates in a vacuum above 600 ° C:

${\displaystyle \mathrm {Cs_{2}CO_{3}\longrightarrow Cs_{2}O+CO_{2}} }$

The standard enthalpy of formation of cesium carbonate is −1148.7 kJ mol ⁻¹ .

use

Cesium carbonate is used as a reagent in a number of organic reactions. Examples are esterification and the formation of macrocycles , in which significantly higher yields can be achieved by using cesium instead of other alkali metal carbonates.

Cesium carbonate can be used as a reagent in protecting group chemistry; it is able to selectively split off an ester group of an aromatic diester. Cesium carbonate is also used as a base in Horner-Wadsworth-Emmons reactions and transition metal - catalyzed reactions.

Other cesium compounds such as cesium azide can be synthesized from cesium carbonate.

Cesium carbonate can be used for the analytical separation of rubidium and cesium because it is easily soluble in ethanol, but rubidium carbonate is hardly soluble.

Individual evidence

1. ↑ ^{a b c d e} data sheet cesium carbonate (PDF) from Merck , accessed on March 15, 2010.
2. ↑ ^{a b} K. A. Hofmann: "Textbook of Inorganic Chemistry", 2nd edition 1919. Verlag F. Vieweg & Sohn, p. 439. Full text
3. ↑ ^{a b} data sheet cesium carbonate from Sigma-Aldrich , accessed on March 15, 2011 ( PDF ).
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-19.
5. ↑ Patent EP0668845 : Process for producing a high-density cesium and rubidium salt solution. Published on August 30, 1995 , inventors: H. Prinz, H. Hofmann, K. Köbele, M. Wegner. ‌
6. ↑ Manfred Bick, Horst Prinz: Cesium and Cesium Compounds . In: Ullmann's Encyclopedia of Industrial Chemistry , Wiley-VCH, Weinheim 2005 ( doi : 10.1002 / 14356007.a06_153 ).
7. ↑ ^{a b c} Timo Flessner, Sven Doye: Cesium carbonate: A powerful inorganic base in organic synthesis . In: Journal for practical chemistry . 1999, 341, 2, pp. 186-190 ( doi : 10.1002 / (SICI) 1521-3897 (199902) 341: 2 <186 :: AID-PRAC186> 3.0.CO; 2-6 ).
8. ^ ^{A b} Jean D'Ans, Ellen Lax: Paperback for chemists and physicists. 3. Elements, inorganic compounds and materials, minerals, Volume 3. 4. Edition, Springer, 1997, ISBN 978-3-540-60035-0 , p. 610f ( limited preview in Google book search).
9. ↑ Fania Moriseevna Perelman: "Rubidium and Cesium", Pergamon Press 1965. P. 46. ( limited preview in the Google book search), doi : 10.1002 / ange.19660780727 .
10. ^ Fritz Blatter, Ernst Schuhmacher: Production of high purity cesium . In: Journal of the beg-Common Metals . 1986, 115, pp. 307-313 ( doi : 10.1016 / 0022-5088 (86) 90153-0 ).