Solvent extraction and separation

In our experiment to produce 2-chloro-2-methylpropane, we reacted an organic compound (2-methylpropan-2-ol) with an aqueous mineral acid (HCl) and produced an organic product (2-chloro-2-methylpropane) and water. At the end of the reaction, the reaction flask probably contained a mixture of these four components, in varying amounts, along with some by-products. The first step towards purification that a chemist normally performs is a solvent extraction and separation. 

The amount of a substance that dissolves in a particular solvent is the solubility of that substance. 

The solubility of a substance is defined as the number of grains of the substance that dissolves in lOOg of solvent under standard conditions. 

Solubility is a physical property, and its value depends on the substance being dissolved, on the solvent and on the temperature. So at any particular temperature, different substances will have different solubilities in the same solvent. We can make use of this fact in the technique of solvent extraction. 

As most reactions are carried out in solution, it is useful to understand a little about solubility. Solubility is related to the molecular structure of both the solute and the solvent. If both are liquids then it is a matter of defining which you call the solvent and which the solute. A compound in a reaction which is not a reactant or a product or a catalyst is said to be the solvent. A liquid component in large excess, may be solvent as well as reactant. 

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Sherikar, A. V. Phalke, P. N. Dhadke, P. M. Solvent extraction and separation studies of platinum using bis(2-ethylhexyl) hydrogen phosphate. Bull. Chem. Soc. Jpn. 1997, 70, 805-808. 

We usually repeat this procedure two or three times during the practice of solvent extraction, and separate the two layers after each vigorous shake (we call this procedure running off the heavier, lower layer of liquid). Several extractions are needed because K(partition) is usually quite small, which implies that only a fraction of the solute is removed from the solution during each partition cycle. 

H.Fr. Schroder, Determination of Fluorinated Surfactants and their Metabolites in Sewage Sludge Samples by LC/MS and MSre after Accelerated Solvent Extraction and Separation on Fluorine Modified RP-Phases, J. Chromatogr. A, in press. 

P-Diketonates. Very strong actinide complexes with p-diketones [An(acac)4 and An02(acac)2] are used in solvent extraction and separation of actinides. They are prepared by direct interaction of the metal or actinyl halide with the appropriate p-diketone in the presence of a base. Only fluorinated An(IV) diketonates produce adducts with Lewis bases, whereas common An02(acac)2 (An = Np, Pu) are stabilized by adduct formation. Fluorinated U02(hfa)2 is a very strong Lewis acid and its adducts with H20 and ROH can be sublimed without decomposition [282],... 

Eujino O, Umetani S, Matsui M. 1994. Determination of uranium in apatite minerals by inductively coupled plasma atomic emission spectrometry after solvent extraction and separation with 3-phenyl-4-benzoyl-5-isoxazolone into diisobutyl ketone. Analytica Chimica Acta 296 63-68. 

Solvents, Extraction and Separation of Pigments. All solvents were freshly glass distilled and ethers were freed of peroxides over highly activated (0% H2O) basic alumina. All procedures were in dim yellow light and extracts/isolates maintained frozen under N2, whenever possible. Chromatographic separation utilized microcrystalline cellulose, Sephadex LH-20, and silica gel in normal and reverse phase modes. Extraction and chromatography is detailed elsewhere (20). 

Step 1. Extraction and separation of the acidic components. Shake 5-10 g. of the sohd mixture (or of the residue R obtained after the removal of the solvent on a water bath) with 50 ml. of pure ether. If there is a residue (this probably belongs to Solubihty Group II or it may be a polysaccharide), separate it by filtration, preferably through a sintered glass funnel, and wash it with a Uttle ether. Shake the resulting ethereal solution in a smaU separatory funnel with 15 ml. portions of 5 per cent, aqueous sodium hydroxide solution until all the acidic components have been removed. Three portions of alkaU are usuaUy sufficient. Set aside the residual ethereal solution (Fj) for Step 2. Combine the sodium hydroxide extracts and wash the resulting mixture with 15-20 ml. of ether place the ether in the ETHER RESIDUES bottle. Render the alkaline extract acid to litmus with dilute sulphuric acid and then add excess of sohd sodium bicarbonate. 

Polyethers are usually found in both the filtrate and the mycelial fraction, but in high yielding fermentations they are mosdy in the mycelium because of their low water-solubiUty (162). The high lipophilicity of both the free acid and the salt forms of the polyether antibiotics lends these compounds to efficient organic solvent extraction and chromatography (qv) on adsorbents such as siUca gel and alumina. Many of the production procedures utilize the separation of the mycelium followed by extraction using solvents such as methanol or acetone. A number of the polyethers can be readily crystallized, either as the free acid or as the sodium or potassium salt, after only minimal purification. 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

A predictive macromolecular network decomposition model for coal conversion based on results of analytical measurements has been developed called the functional group, depolymerization, vaporization, cross-linking (EG-DVC) model (77). Data are obtained on weight loss on heating (thermogravimetry) and analysis of the evolved species by Eourier transform infrared spectrometry. Separate experimental data on solvent sweUing, solvent extraction, and Gieseler plastometry are also used in the model. 

That benzene hexachloride isomer mixture is then the raw material for lindane production. The production of lindane per se is not a chemical synthesis operation but a physical separation process. It is possible to influence the gamma isomer content of benzene hexachloride to an extent during the synthesis process. Basically, however, one is faced with the problem of separating a 99%-plus purity gamma isomer from a crude product containing perhaps 12 to 15% of the gamma isomer. The separation and concentration process is done by a carefully controlled solvent extraction and crystallization process. One such process is described by R.D. Donaldson et al. Another description of hexachlorocyclohexane isomer separation is given by R.H. Kimball. 

Extractions and separations in two-phase systems require knowledge of the miscibilities and immiscibilities of ILs with other solvents compatible with the process. These are most usually IL/aqueous biphase systems in which the IL is the less polar phase and organic/IL systems in which the IL is used as the polar phase. In these two-phase systems, extraction both to and from the IL phase is important. 

The very extensive changes that have taken place over recent years and the broad application to organic separations necessitated a major revision of Part C covering solvent extraction and chromatographic procedures. These particular... 

Purified extracts contain higher contents of tea catechins obtained by further purification processes, for example solvent extraction or column chromatography techniques (Takeo, 2001). New techniques, such as membrane extraction and separation, may be beneficial in producing such extracts (Nwuha, 2000, Wang et al, 1995). 

Co (I I) complex formation is the essential part of copper wet analysis. The latter involves several chemical unit operations. In a concrete example, eight such operations were combined - two-phase formation, mixing, chelating reaction, solvent extraction, phase separation, three-phase formation, decomposition of co-existing metal chelates and removal of these chelates and reagents [28]. Accordingly, Co (I I) complex formation serves as a test reaction to perform multiple unit operations on one chip, i.e. as a chemical investigation to validate the Lab-on-a-Chip concept. 

Extraction and Separation of Alkaloids - The air-dried ground heart-wood (2.2 kg) was extracted by percolation at room temperature with alcohol USP until a negative alkaloid test of the percolate was observed. Removal of the solvent at reduced pressure and at 40° left 71 g of residue that exhibited antimicrobial activity. A 35 g sample of the alcohol-soluble residue was partitioned between 125 ml each of ether and 2Z citric acid In water. The ether layer was extracted twice more with 125 ml of 2% citric acid, filtered to remove some lnterfaclal solids (5.8 g alkaloid negative, no antimicrobial activity), dried (sodium sulfate), and evaporated to dryness, giving 8.6 g of ether solubles that had no antimicrobial activity. 

Distillation is probably the most widely used separation technique in the chemical process industries, and is covered in Chapter 11 of this volume, and Chapter 11 of Volume 2. Solvent extraction and the associated technique, leaching (solid-liquid extraction) are covered in Volume 2, Chapters 13 and 10. Adsorption, which can be used for the separation of liquid and gases mixtures, is covered in Chapter 17 of Volume 2. Adsorption is also covered in the books by Suziki (1990) and Crittenden and Thomas (1998). 

Singh, R. Khwaja, A. R. Gupta, B. Tandon, S. N. Extraction and separation of nickel(II) using bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301) and its recovery from spent catalyst and electroplating bath residue. Solvent Extr. Ion Exch. 1999, 17, 367-390. 

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