Separations, by aqueous extractions

Not pure separated by aqueous extraction of the frozen paste. Not pure separated by eleetrodialysis. 

The resulting 6-(methylthio)hexanoic acid is easily separable by aqueous extraction or by filtration through silica gel and can be reoxidized to 1873 with sodium metaperiodate in 97% yield. Low temperature (—60 °C) NMR spectrometry has been used to examine the intermediates of this Swem process. The results indicate that any residual unoxidized alcohol is generated during Pummerer elimination of the alkoxysulfonium intermediate and can be minimized by prolonged exposure to triethylamine at —40 °C. Reaction of the potassium salt of 1873 with cross-linked chloromethyl polystyrene affords a polymer-bound reagent that quantitatively oxidizes bomeol to camphor when used in two-fold excess [1394]. 

It was found that the heating of an aminophosphine oxide in the presence of bromine in chloroform led to a mixture of an ammonium salt and diphenylphosphinoyl bromide. After treatment with methanol and a subsequent separation by aqueous extraction, methyl diphenylphosphinate and a quinolinecarbaldehyde were formed (Scheme 37). " ... 

Nickel and Cobalt. Often present with copper in sulfuric acid leach Hquors are nickel [7440-02-0] and cobalt [7440-48-4]. Extraction using an organophosphoric acid such as D2EHPA at a moderate (3 to 4) pH can readily take out the nickel and cobalt together, leaving the copper in the aqueous phase, but the cobalt—nickel separation is more difficult (274). In the case of chloride leach Hquors, separation of cobalt from nickel is inherently simpler because cobalt, unlike nickel, has a strong tendency to form anionic chloro-complexes. Thus cobalt can be separated by amine extractants, provided the chloride content of the aqueous phase is carefully controUed. A successhil example of this approach is the Falcon-bridge process developed in Norway (274). 

To provide a more generalized picture for achieving separations by solvent extraction one can consider a number of possibilities, according to direction of transfer. Such possibilities are (i) pre-extraction (aqueous — solvent) (ii) extraction (aqueous — solvent), scrubbing (solvent —> aqueous) (iii) stripping/back extraction (solvent — aqueous) and (iv) solvent clean up (solvent —> aqueous — solvent). The direction of transfer has been shown in the parentheses of the four possibilities that have been listed. A reference to Figure 5.14 is relevant in this premise. 

Drugs have been purified by SPE in the analysis of amphetamine (AM) by Kaleta et al. [98], by various consecutive washing steps with hexane in the analysis of methamphetamine (MA) by Jones-Lepp and Stevens [99], and by simple centrifugation after addition of water, to separate the aqueous extract from a bottom sediment layer and a top fat layer, in the analysis of AM, MA, cocaine (CO), and benzoylecgonine (BE) by Langford et al. [100], who found little improvement in reducing matrix effects when applying SPE cleanup. 

The Anelli oxidation of alcohols to aldehydes and ketones has been accomplished using polymer-supported nitroxyl radical catalysts. The practicality of removing polymer-supported reagents by filtration to simplify product purification is highlighted by these examples. Bolm and coworkers11 demonstrated that a silica-supported nitroxyl catalyst is easily filtrated after use from the reaction solution, recovered and recycled, and the residual inorganic salts present in the reaction mixture are separated from the organic product by aqueous extraction (Table II, entry 7). 

The selective extraction of a radioactive nuclide as a nonpolar compound or complex from an aqueous solution by an immiscible organic solvent Is frequently the most satisfactory method for making a fast radiochemical separation In either macro or trace concentrations. Separations by solvent extraction are simple, convenient, clean, and rapid. They usually require apparatus as uncomplicated as a separatory funnel and may readily be adapted to remote handling procedures. 

Examples of thenoyltrifluoroacetone (TTA) (in benzene) extraction can be found in the separation of. 3.8-minute V 2 in. neutron activation analysis (90), of zirconium activities in niobium bombarded by protons (128), and of 1.8-minute Pa22 from the reaction products of thorium bombarded.by a cyclotron (172,173,175)- 16-second Y89"1 (109) and 25-minute Am246 (74), the daughter products of Zr and Pu2 respectively, were separated by back extraction into acidic aqueous solution from the parent in TTA-benzene solution. 

Chemex [Chemical exchange] A process for separating uranium isotopes, based on the equilibrium between U3+ and U4+ in aqueous solution. U-238 concentrates in the LP+ state and U-235 in the U4+. Uranium in the two valence states is separated by solvent extraction into tributyl phosphate. Developed and piloted in France but not commercialized. 

Dimethyl sulfate (38.4 g., 0.30 mole) is added slowly [Caution— toxic substance) with stirring to a solution of 44 g. (0.26 mole) of 7B-bromophenol (p. 54) in 107 g. of a 10% aqueous solution of sodium hydroxide. Stirring is continued until the reaction mixture is neutral. The organic layer is separated by ether extraction, and the ethereal solution is dried. Distillation gives a colorless oil, b.p. 209-212°/752 mm. This is redistilled and 35 g. (73%) of m-bromoanisole is collected at 210-211 . 

Separation by solvent extraction Uranium can be extracted from aqueous solutions using extraction agents into the solvent phase, from which it can be stripped. The extraction agents used are phosphorus compounds such as di-(2-ethylhexyl)-phosphate, tri-n-butyl-phosphate and tri-n-octylphosphine oxide as well as primary, secondary and tertiary amines in salt form or as quaternary ammonium salts. The extraction agents are diluted with inert hydrocarbons, preferably kerosene, to concentrations of 4 to 10% by volume. The solubility of the amine salts, particularly the hydrogen sulfates, chlorides and nitrates is increased by adding long chain alcohols (e.g. isodecanol). 

One possibility is a support bearing a functional group that is responsible for a phase switch of the impurities, thereby allowing subsequent separation of product and by-product by aqueous extraction or simple filtration. 

Partitioning of neptunium. Uranium and tetravalent neptunium in the extract are separated by fractional extraction with 0.5 M HNO3. The less extractable Np(IV) is returned to the aqueous phase while uranium remains in the solvent, from which it can be stripped with 0.01 AfHNOa (not shown). 

The fusion of a mixture of ammonium fluoride and phosphorus pentoxide leads to both mono-and difluoro salts (5.269). The monofluoro salt can be separated by ethanol extraction and precipitated as the silver salt. Aqueous solutions of KPO3F are easily hydrolysed with caustic potash to form the monofluoro salt and potassium fluoride (5.270). 

Thus, two water-insoluble organic compounds, HA, which is acidic, and N, which is neutral, that are dissolved in an organic solvent may be separated by selectively extracting the acidic compound into a basic aqueous phase. After the aqueous and organic phases are separated, HA is recovered from the aqueous phase upon neutralization, and N is obtained by removing the organic solvent (Fig. 5.1). 

Caffeine is readily soluble in hot water, because the alkaloid is often bound in thermally labile, partially ionic complexes with naturally occurring organic acids, such as with 3-caffeoylquinic acid in the coffee bean. For this reason it is relatively easy to separate caffeine from black tea leaves by aqueous extraction. 

Stable joining of protein to nucleic acid can be demonstrated by several procedures. Perhaps the easiest approach is a simple phenol extraction method that gives accurate and reproducible results. This method is based on the observation that proteins and nucleic acids ordinarily can be separated by phenol extraction protein migrates into the phenol layer whereas nucleic acids remain in the aqueous phase. However, upon linkage of a tRNA to a synthetase the nucleic acid migrates with the protein into the phenol layer. A similar observation was made earlier by Markovitz, who showed that DNA cross-linked to DNA polymerase is also extracted into phenol. ... 

Similarly, it is possible to make an epoxide from an alkene in flow using H2O2 with an oxometallate catalyst (47% atom efficient) and is much preferred to mCPBA epoxidation (9% atom efficient) in which byproduct separation is by aqueous extraction which all becomes waste (Scheme 12.3). ... 

To separate two compounds in an aqueous extraction, one must be water soluble (or be able to be converted into a water-soluble ionic compound by an acid-base reaction), and the other insoluble. 1-Octanol has greater than 5 C s, making it insoluble in water. Octane is an alkane, also insoluble in water. Neither compound is acidic enough to be deprotonated by a base in aqueous solution. Since their solubility properties are similar, they cannot be separated by an extraction procedure. 

If the organic compound which is being steam-distilled is freely soluble in water, an aqueous solution will ultimately collect in the receiver F, and the compound must then be isolated by ether extraction, etc. Alternatively, a water-insoluble compound, if liquid, will form a separate layer in F, or if solid, will probably ciystallise in the aqueous distillate. When steam-distilling a solid product, it is sometimes found that the distilled material crystallises in E, and may tend to choke up the condenser, in such cases, the water should be run out of the condenser for a few minutes until the solid material has melted and been carried by the steam down into the receiver. 

Place the distillate in a separating-funnel and extract the benzonitrile twice, using about 30 ml. of ether for each extraction. Return the united ethereal extracts to the funnel and shake with 10% sodium hydroxide solution to eliminate traces of phenol formed by decomposition of the benzenediazonium chloride. Then run off the lower aqueous layer, and shake the ethereal solution with about an equal volume of dilute sulphuric acid to remove traces of foul-smelling phenyl isocyanide (CaHjNC) which are always present. Finally separate the sulphuric acid as completely as possible, and shake the ether with water to ensure absence of acid. Run off the water and dry the benzonitrile solution over granular calcium chloride for about 20 minutes. 

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