Caesium carbonate

White odorless solid

4.07 g · cm -3

610 ° C.

• Good in water ( 2615 g · l-1 at 15 ° C )
• Well in ethanol

Attention

2333 mg · kg -1 ( LD50, rat, oral)

-1139.7 KJ / mol

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

Production and representation

Cesium can be obtained from pollucite / spodumene concentrates. To this end, this is for example under pressure with a calcium hydroxide solution at 220 ° C heated ( hydrothermal ). After filtration of insoluble calcium silicates, precipitation of excess calcium and minerals present in the lithium salts with carbon dioxide as carbonate, remains an alkaline cesium carbonate. This may then be neutralized, for example with sulfuric acid. There is formed a cesium aluminum alum which is further purified by recrystallization. For this salt cesium hydroxide is then again made ​​that will ultimately be implemented by means of carbon dioxide to pure cesium.

Properties

Cesium carbonate is hygroscopic and readily dissolves in water. Aqueous Caesiumcarbonatlösungen react similarly to other alkali metal alkaline. In contrast to other alkali metal in addition to the expensive rubidium cesium is also soluble in many organic solvents. Cesium carbonate crystallizes in the monoclinic crystal system, space group P21 / c with lattice parameters a = 612.64 pm, b = 1027.65 pm, c = 814.76 pm, β = 95.85 ° and four formula units per unit cell. Is dissociated in the vacuum above 600 ° C:

The standard enthalpy of cesium carbonate is -1148.7 kJ · mol -1.

Use

Cesium carbonate is used in a series of organic reactions as reagent. Examples are esterifications and the formation of macrocycles, where instead of the other alkali metal carbonates, cesium much higher yields can be achieved by the use of.

Cesium carbonate can be used as a reagent in the protective group chemistry; it is capable of selectively cleaving an ester group of an aromatic diester. Further cesium carbonate is used as base in the Wittig-Horner reactions and transition metal - catalyzed reactions.

Other cesium compounds as Caesiumazid can be synthesized from cesium.

Cesium can be used for the analytical separation of rubidium and cesium, as it is readily soluble in ethanol, rubidium but is sparingly soluble.