Carboxylic acids solvent extraction

The tetrahydrocannabinol carboxylic acid was extracted from the urine by means of a solid state extraction cartridge packed with a Cl 8 reverse phase (octyldecyldimethyl chains). As the urine sample was used direct, and contained no added solvent, the materials of interest were irreversibly adsorbed on the reverse phase solely by dispersive interactions. 

Usually extractions are carried out at room temperature, primarily for convenience extractions at higher temperatures may allow for smaller solvent volumes to be used, due to the increased solubility of compounds at higher temperatures. In the isolation of the phosphinyl carboxylic acid 8, extractions were carried out... 

It requires a certain flexibility of mind to accept the proposal of using the same THF as extraction solvent in some cases. Ue discovered this possibility, when we tried to remove this solvent from carboxylic acids in a water-pump, vacuum it appeared difficult to remove the last traces of this solvent, even when heating at 70-80°C in a vacuum of 10-15 mmHg was applied. It seemed that there is some weak complexation. This led us to the idea of using THF for the extraction of carboxylic acids from the aqueous phase (after saturation with... 

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. 

Typical nonsieve, polar adsorbents are siUca gel and activated alumina. Kquilihrium data have been pubUshed on many systems (11—16,46,47). The order of affinity for various chemical species is saturated hydrocarbons < aromatic hydrocarbons = halogenated hydrocarbons < ethers = esters = ketones < amines = alcohols < carboxylic acids. In general, the selectivities are parallel to those obtained by the use of selective polar solvents in hydrocarbon systems, even the magnitudes are similar. Consequendy, the commercial use of these adsorbents must compete with solvent-extraction techniques. 

A mixture of 17 g of the methiodide and 32 ml of a 40 % aqueous potassium hydroxide solution is heated with stirring in a flask fitted with a condenser. The heating bath should be kept at 125-130°, and the heating should be continued for 5 hours. The cooled reaction mixture is then diluted with 30 ml of water and washed twice with 25-ml portions of ether. The aqueous layer is cautiously acidified in the cold with concentrated hydrochloric acid to a pH of about 2 and then extracted five times with 25-ml portions of ether. The combined extracts are washed twice with 10% sodium thiosulfate solution and are dried (magnesium sulfate). Removal of the solvent followed by distillation affords about 3 g of 4-cyclooctene-l-carboxylic acid, bp 125-12671-1 mm. The product may solidify and may be recrystallized by dissolution in a minimum amount of pentane followed by cooling in a Dry-Ice bath. After rapid filtration, the collected solid has mp 34-35°. 

To a suspension of 12.0 grams of 3-methylflavone-8-carboxylic acid in 200 ml of anhydrous benzene Is added 10.0 grams of thionyl chloride. The mixture is refluxed for 2 hours during which the suspended solid goes into solution. The solvent is completely removed by distillation, the residue extracted with benzene and the extract evaporated to dryness. The product, 3-methylflavone-8-carboxylic acid chloride, is recrystallized from ligroin to give crystals melting at 155° to 156°C. 

The analytical method described is also used in following the consumption of peroxybenzoic acid or other peroxy acids during an oxidation reaction it has also been used in determining the conversion of other carboxylic acids to peroxy acids when solvent extraction has been used in the isolation. 

Here we shall confine ourselves to the solvents benzene and 1,2-dichloroethane (class 8). Considering benzene, many investigators have demonstrated since the 1930s the feasibility of titrations in this solvent using both potentiometric and spectrophotometric methods, paying much attention to acid-base indicator reactions under the influence of primary, secondary and tertiary amines. Association of carboxylic acids in benzene was studied at a later stage, mainly on the basis of colligative properties, IR spectroscopy and solvent extraction. ... 

Preston, J. S. du Preez, A. C. Separation of nickel and calcium by solvent extraction using mixtures of carboxylic acids and alkylpyridines. Hydrometallurgy 2000, 58, 239-250. 

Preston, J. S. Solvent extraction of metals by carboxylic acids. Hydrometallurgy 1985, 14, 171-188. 

In ODS, sulfur compounds present in fuels are oxidized to more polar sulfones / sulfoxides to facilitate their removal by solvent extraction or adsorption. Various oxidation systems have been reported in the literature for this transformation. Among these oxidants like hydrogen peroxide (H2O2) and carboxylic acid as catalyst3"5. For the chemical industry, it becomes more and more important to develop cleaner technologies. Solvent extraction processes are used to separate sulfones / sulfoxides from oxidized fuels. These processes required suitable and selective solvents for separation of oxidized sulfur compounds from petroleum feedstocks. 

We, at IIP carried out certain oxidation studies and report the results on oxidation of sulfur compounds present in gas oil using carboxylic acid / H2O2 system. Extent of sulfur removal in gas oil after oxidative desulfurization was monitored by sulfur analysis. Oxidation and solvent extraction reduced sulfur in gas oil from 1.5% to 0.20% in single stage batch extractor. 

However, morpholine-4-carboxylic acid 2-hydroxy-1-methyl-ethyl ester is formed by the reaction of PC and the substrate morpholine in an undesired side reaction. By use of 1.4-dioxane or the pyrrolidones as mediator s3 about 30 to 45% of the morphoUne is consumed by this side reaction. The by-product is contained in the PC phase and can not be extracted to the non-polar product phase. The selectivity to the desired amines is lowered, because of the consiunption of the morphoUne. Thus, PC has to be substituted by another polar solvent (e.g. water, methanol or ethylene glycol) in future experiments. The lactates react with the morphoUne, too resulting in the corresponding amide. Overall, the hydroaminomethylation in the TMS systems PC/dodecane/lactate results in a conversion of 1-octene of about 80%, but in selectivities to the amines of only 50 to 60%. 

Soluble loss of a reagent (extractant, modifier, or diluent) from the solvent phase is an inherent part of the solvent extraction process, since all organic compounds are soluble, to some extent, in water. The conditions prevailing in the system can also promote solubility, which can be a particular problem if the composition and properties of the aqueous phase are inflexible. For example, the solubility of alkylphosphoric acid and carboxylic acid extractants is dependent on temperature, pH, and salt concentration in the aqueous phase. 

Under conditions of low salt concentration in the aqueous phase, and above a pH 6, the solubility of these acids is economically prohibitive. Even at lower pH values, the solubility could be considered high from the point of view of pollution. For a C7-C9 fraction of aliphatic mono-carboxylic acids, the solubility in water as a function of concentration in the solvent phase is shown in Fig. 7.9 [14]. Here again, complete information is unavailable, since no reference is made to pH or salt concentration. Presumably, the pH is in the range 4-6. However, it is interesting to note the rapid increase in solubility in the aqueous phase as the extractant concentration is increased. This effect also applies to other extractants. 

Method B (general procedure)7 To an NaHTe solution, prepared from tellurium powder (1.27 g, 10 mmol) and NaBH4 (0.9 g, 24 mmol) in absolute EtOH (25 mL), is added the 2-haloethyl ester (10 mmol) in EtOH (5 mL). (The reaction takes place instantaneously for 2-bromoethyl esters at room temperature.) The mixture is stirred for 1 h, then acidified with dilute HCl, extracted with ether and the organic phase dried and evaporated. The residue is recrystalUzed from appropriate solvents to give pure carboxylic acids. 

Considerable efforts have centered on carrying out the synthesis of polybenzimidazoles at more moderate temperatures. Polymerization of the isophthalic acid or its diphenyl ester have been successfully carried out in polyphosphoric acid or methanesulfonic acid-phosphorous pentoxide at 140-180°C, but the reaction is limited by the very low solubilities (<5%) of the reactants in that solvent. The lower reaction temperature is a consequence of activation of the carboxyl reactant via phosphorylation. Lower reaction temperatures are also achieved in hot molten nonsolvents such as sulfolane and diphenyl sulfone, but the need to remove such solvents by a filtration or solvent extraction is a disadvantage. 

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