Carboxylic acid separation from other organic

A carboxylic acid can be separated from other organic compounds by converting it to a water-soluble carboxylate anion by an acid-base reaction. 

In a similar manner, carboxylic acid anions, phenolates, etc. can be separated from other organic matter by retention on a small anion exchanger in the OH form. 

The separation of pyrrolidone carboxylic acid from other organic... 

Carboxylic acids are weak acids in aqueous solution, forming an equilibrium between the free acids and the carboxylic ion. In the presence of a base like sodium hydroxide or sodium hydrogen carbonate, they ionise to form water-soluble salts and this provides a method of separating carboxylic acids from other organic compounds. 

Carboxylic acid chlorides from carboxylic acids and 2,2,2-trichloro-l,3,2-benzodioxa-phosph(v)ole 1127 A mixture of the acid (0.02 mole) and the trichloride (0.02 mole) is heated and the acid chloride is then separated by distillation. Yields are acetyl chloride 67% (after 30 min at 100° b.p. 50-51°) benzoyl chloride 81 % (after 60 min at 100° b.p. 82-85°/ll mm) chloroacetyl chloride 77% (after 30 min at 150° b.p. 105-108°). In other cases the reaction mixture can be diluted with ether, poured on ice, and well shaken therewith the aqueous phase should be extracted again with ether, the organic phases then being washed with sodium hydrogen carbonate solution and with water and dried over Na2S04, the ether removed, and the residue distilled. 

Xiao-Hua Yang et al. [ 1 ] determined nanomolar concentrations of individual low molecular weight carboxylic acids (and amines) in seawater. Diffusion of the acids across a hydrophobic membrane was used to concentrate and separate carboxylic acids from inorganic salts and most other organic compounds prior to the application of ion chromatography. Acetic propionic acid, butyric-1 acid, butyric-2 acid, valeric and pyruvic acid, acrylic acid and benzoic acid were all found in reasonable concentrations in seawater. 

Working up of the reaction mixture varies according to the nature of the reduction product. If the product is volatile with steam, the reaction mixture is made alkaline and the product separated hy steam distillation. In other cases, the reaction mixture is filtered with suction after having been made alkahne. Then water or alkali soluble amino compounds, especially sulfom c and carboxylic acids, are found in the filtrate, from which they may be isolated by acidifying, salting out, or evaporation. Alkali insoluble bases remain in the iron sludge and must be separated from it by extraction with a suitable organic solvent. Frequently the reduction mixture, after removal of the iron, can be used directly in the next step without isolation of the reduction product. 

Isolation. Isolation procedures rely primarily on solubility, adsorption, and ionic characteristics of the p-lactam antibiotic to separate it from the large number of other components present in the fermentation mixture. The penicillins are monobasic carboxylic acids which lend themselves to solvent extraction techniques (154). Pencillin V, because of its improved acid stability over other penicillins, can be precipitated direcdy from broth filtrates by addition of dilute sulfuric acid (154,156). The separation process for cephalosporin C is more complex because the amphoteric nature of cephalosporin C precludes direct extraction into organic solvents. This antibiotic is isolated through the use of a combination of ion-exchange and precipitation procedures (157). The use of neutral, macroporous resins such as XAD-2 or XAD-4, allows for a more rapid elimination of impurities in the initial steps of the isolation (158). The isolation procedure for cephamycin C also involves a series of ion exchange treatments (103). 

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