Cesium carbonate is an inorganic compound. White solid at room temperature and pressure. It is soluble in water and absorbs moisture quickly when exposed to air. Cesium carbonate aqueous solution is strongly alkaline and can react with acid to form the corresponding cesium salt and water, and release carbon dioxide. Cesium carbonate should be sealed, dried and kept separate from acid during storage.
Preparation and synthesis:
1. Prepare sulfuric acid solution of cesium salt, add aluminum sulfate to it, and precipitate cesium aluminum alum. Weigh 250 grams of cesium bauxite and dissolve it in 2.5 liters of boiling water. When cooled slowly, the alum recrystallizes. Purification The above operations are purified and filtered to obtain the purified product of cesium alum. After mixing it into an aqueous solution, excess barium hydroxide is added to it. Cesium carbonate can be prepared by putting carbon dioxide gas into the filtrate, filtering it, and then continuing to put carbon dioxide gas into the filtrate.
2. Weigh appropriate amount of cesium chloride in a borosilicate glass container, add excess nitric acid, remove chlorine, remove the nitrate produced by the reaction, put it into a platinum dish, add four times the amount of crystalline oxalic acid. The reaction yields oxalate, which is then calcined to produce cesium carbonate.
3. Produced by the reaction of cesium hydroxide and carbon dioxide.
Many of the properties of cesium carbonate in organic synthesis are due to the soft Lewis acidity of cesium ions, making them soluble in organic solvents such as ethanol, DMF and ether.
Better solubility in organic solvents allows cesium carbonate as an effective inorganic base for palladium-catalyzed chemical reactions such as Heck, Suzuki and Sonogashira reactions. For example, with the support of cesium carbonate, the Suzuki cross-coupling reaction yields 86%, compared with 29% and 50% for the same reaction with sodium carbonate or triethylamine. Similarly, in the Heck reaction of methacrylate and chlorobenzene, cesium carbonate shows a very clear advantage over other inorganic bases (such as potassium carbonate, sodium acetate, triethylamine and potassium phosphate). Cesium carbonate is also very important in achieving o-alkylation of phenolic compounds. It is speculated that the alkylation of phenol O in cesium carbonate induced non-aqueous solvents may lead to the formation of phenoxy anions. Therefore, alkylation of secondary halides with high activity which can be easily eliminated may also occur. Cesium carbonate also has important applications in the synthesis of natural products.
In the key step of the closed-loop reaction for the synthesis of lipogrammistin-a compounds, cesium carbonate is used as an inorganic base to obtain closed-loop products with high yield. In addition, cesium carbonate also has important applications in solid-supported organic reactions due to its good solubility in organic solvents.
In a carbon dioxide atmosphere, a three-component reaction of aniline and a solid-phase loaded halogen compound is induced to yield carboxylate or carbamate compounds at high yields. Cesium carbonate can also be used as a base under microwave radiation to achieve esterification of benzoic acid and solid supported halogenated compounds.