Potassium carbonate hydrogencarbonate

In one process the carbon dioxide is removed using potassium carbonate solution, potassium hydrogencarbonate being produced ... 

Potassium chloride is reacted with carbon dioxide in precarbonated isopropylamine solution under pressure in an autoclave. Potassium hydrogencarbonate precipitates and the amine is converted into isopropylamine chlorohydrate. The potassium salt is isolated by filtration, washed free of amine and heated to convert it to the carbonate. Unreacted amine present in the filtrate is recovered by distillation. Hydrated lime is then added to convert the isopropylamine chlorohydrate back to the amine, which is also recovered by distillation. The main uses of potassium carbonate are the production of glass and sodium silicate. 

Tilak et described the use of excess mixed carbonic anhydrides to force condensation reactions to completion followed by the destruction of the excess mixed anhydride via the addition of aqueous potassium hydrogencarbonate. Hydrolysis of the nnixed anhydride was rapid and the resulting protected dipeptide could be extracted into ethyl acetate in a high state of purity, leaving the excess amino acid derivative and the salts in the aqueous phase. Without further purification the protected dipeptide was N -deprotected and reacted with the next mixed anhydride, and the process repeated until the desired peptide was obtained. Beyerman et al. substantially expanded the scope of this procedure and named it the REMA method for peptide synthesis (Repetitive Excess Mixed Anhydride).P°1 These reaction conditions provide an excellent method to ensure complete reaction of the amine component as well as rapid reaction rates and minimal side products. However, care must be taken to ensure that the excess carboxylic acid component is soluble in sodium hydrogencarbonate solution, e.g. when Z-Asp(OBzl)-OH is the acid component, it is extracted into the ethyl acetate as the sodium salt along with the product. With the due precautions the yields of small peptides are so high that the method could be applied without purification of the intermediate products, that is, in a repetitive way. 

The nmr chemical shifts of alkah metal ( K, Na etc.) phenoxide moved to down field upon formation of the complex, [ phenoxide-M CO2] with carbon dioxide in the Kolbe-Schmitt reaction. The complex formed under pressure of carbon dioxide showed more increments in weights and chemical shifts, as much as 0.72 ppm of (5 paia of potassium phenoxide at 5 MPa. The kinetic studies on the carboxylation of resorcinol in aqueous hydrogencarbonates with carbon dioxide revealed an equilibrium between resorcinol and the product or resorcylic acid. 

The powdered alkali metal (K, Na etc.) phenoxide (ca.O.lg) was placed in a vial fLUed with carbon dioxide, and covered with parafihn. Carbon dioxide of purity more than 99.95% was supplied through a capillary tubing at room temperature. After the absorption of the gas, the weight increment was measured, and a portion of the sample was transferred in an nmr tube of 5 mm and dissolved in DMF with acetone-de, or in DMSO-d with addition of TMS. The nmr spectra on a JEOL-JNM GX 270 spectrometer were taken without delay. For the kinetic studies, a 150 mL aqueous solution containing resorcinol and potassium hydrogencarbonate was kept at 80 C with or without bubbling carbon dioxide, then an ahquot was taken at given time for nmr and/or HPLC analyses. ... 

The rate of the formation of /3 -resorcylic acid (RA) was a first order with respect both to ROH and to KHCOi. The overall reaction rate with bubbling carbon dioxide gas into the aqueous solution of potassium hydrogencarbonates is d[resorcylic acidj/dt = ki[resorcinol][KHCO,d + k2[resorcinol][pC02] ( 1)... 

Sodium and potassium hydrogencarbonates are less soluble than the carbonates. Magnesium, calcium, strontium and barium hydrogencarbonates exist only in solution. Attempts to remove the water destroy the compounds ... 

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