Acetylacetone, solvent extraction

If a neutral chelate formed from a ligand such as acetylacetone is sufficiently soluble in water not to precipitate, it may stiH be extracted into an immiscible solvent and thus separated from the other constituents of the water phase. Metal recovery processes (see Mineral recovery and processing), such as from dilute leach dump Hquors, and analytical procedures are based on this phase-transfer process, as with precipitation. Solvent extraction theory and many separation systems have been reviewed (42). 

Other fluorinated derivatives of acetylacetone are trifluoroacetylacetone (CF3COCH2COCH3) and hexafluoroacetylacetone (CF3COCH2COCF3), which form stable volatile chelates with aluminium, beryllium, chromium(III) and a number of other metal ions. These reagents have consequently been used for the solvent extraction of such metal ions, with subsequent separation and analysis by gas chromatography [see Section 9.2(2)]. 

Sample. The solvent extraction of aluminium from aqueous solution using acetylacetone can provide a suitable sample solution for gas chromatographic analysis. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

Solvent extraction has become a common technique for the determination of formation constants, P , of aqneons hydrophilic metal complexes of type MX , particularly in the case when the metal is only available in trace concentrations, as the distribntion can easily be measnred with radioactive techniques (see also section 4.15). The method reqnires the formation of an extractable complex of the metal ion, which, in the simplest and most commonly used case, is an nn-charged lipophilic complex of type MA. The metal-organic complex MA serves as a probe for the concentration of metal ions in the aqueous phase through its equilibrium with the free section 4.8.2. This same principle is used in the design of metal selective electrodes (see Chapter 15). Extractants typically used for this purpose are P-diketones like acetylacetone (HAA) or thenoyltrifluoroacteone (TTA), and weak large organic acids like dinonyl naph-talene sulphonic acid (DNNA). 

Albinsson, Y. Development of the AKUFVE-LISOL Technique. Solvent Extraction Studies of Lanthanide Acetylacetonates. Diss. Chalmers Univ. Techn., Gothenburg (1988). 

Cr(VI) is a toxic element, and its environmental pollution should be monitored even in seawater. CrO - is a stable chemical species in seawater, while Cr(III) also exists in relatively high amounts. Therefore, a separation of Cr(VI) from Cr(III) is necessary in the analysis of Cr( VI). For this purpose, the solvent extraction technique can also be used, being followed by atomic absorption analysis. Many workers have investigated the solvent extraction of total Cr in seawater, where Cr was extracted with acetylacetonate, DDC, APDC and analysed by AAS [37—42]. Hiiro et al. examined in detail the separation of Cr(VI) from Cr(III) in seawater [42]. The effect of pH values on extraction of Cr(VI) is shown in Fig. 5. Cr( VI) is most effectively extracted near pH 5, while Cr(III) is increasingly extracted above pH 4. Therefore,... 

Moffett J. W. and Zika R. G. (1987) Solvent extraction of copper acetylacetonate in studies of copper (II) speciation in seawater. Mar. Chem. 21, 301-313. 

Y. Albinsson, Solvent extraction studies of lanthanide acetylacetones, Acta Chem. Scand., 43 (1989) 919. 

Moffett, J.W., and R.G. Zlka. Solvent extraction of copper acetylacetonate In studies of copper speclatlon In seawater, (submitted). 

Tetrasodium EDTA Trisodium EDTA catalyst, sealants Triethylene diamine catalyst, shoe soles Diazabicycloundecene catalyst, SHOP process Nickel chloride hexahydrate catalyst, silicone elastomers Dibutyltin dilaurate catalyst, silicone rubber curing Bis (2,4-dichlorobenzoyl) peroxide catalyst, silicone rubber 2-component Chloroplatinic acid catalyst, slabstock N,N,N -Trimethyl-N -hydroxyethylbisaminoethylether catalyst, SO2 oxidation Cesium sulfate catalyst, solder fluxes Isooctyl acid phosphate catalyst, soldering fluxes Ethyl acid phosphate 2-Ethylhexyl phosphate Stearyl acid phosphate catalyst, solid fuels Ferric acetylacetonate catalyst, solid rocket fuels Copper nitrate (ic) catalyst, solvent extractants Ethyl acid phosphate 2-Ethylhexyl phosphate Stearyl acid phosphate catalyst, solvent hydrogenation beer-making hops... 

The solvent extraction of metal-chelate complexes for trace analysis of water samples has been briefly reviewed (473). Concentration factors of less than 1000 are to be expected because of the need to handle reasonable quantities of organic solvent. However, since not all of the organic solvent sample is used in the analysis, this results in a less than optimal use of the system. An excellent batch-extraction apparatus recently has been described (474) for the extraction of organic substances from water. Concentration factors of more than 10,000 were easily obtained if organic volumes of 100 /w, or less, which were used to extract 1 liter of solution, could be fully analyzed (eg., by AAS). A useful system has been described (475) which combines three chelating agents (dithizone, 8-hydroxyquinoline, and acetylacetone) and quantitatively collects Al, Be, Cd, Co, Cu, Fe, Pb, Ni, Ag, and Zn in one extraction at a pH of 6. 

A number of organic compounds, eg, acetylacetone [123-54-6] and cupferron [135-20-6] form compounds with aqueous actinide ions (IV state for reagents mentioned) that can be extracted from aqueous solution by organic solvents (12). The chelate complexes are especially noteworthy and, among these, the ones formed with diketones, such as 3-(2-thiophenoyl)-l,l,l-trifluoroacetone [326-91-0] (C4H2SCOCH2COCF2), are of importance in separation procedures for plutonium. 

The acetylacetone complex Be(acac)2 is a neutral compound with an organic ligand, and hence is extractable from HOH into immiscible non-aqueous solvents such as benzene, carbon tetrachloride, chloroform, and diethylether. 

Extraction of the rare earths with acetylacetone has been investigated [418, 419] and is found to be enhanced by the decreasing basicity of the rare earth ions. The gas chromatographic separation of rare earth complexes with 2,2,6,6-tetramethyl-3,5-heptanedione has already been mentioned. The acetylacetonate complexes of the rare earths are reported to exist as either anhydrous [420, 421], mono- [422], di- [422] or trihy-drates [422, 423], Stites et al. [424] have studied the pH of the precipitation of several rare earth acetylacetonates and reported the melting points of the complexes. The europium acetylacetonate precipitated at pH 6.5, and melted at 144—45° C. The existence of monomers and dimers for these complexes in nonaqueous solvents has been proposed [421, 425-427],... 

Ail equimolar mixture (10 mmol) of benzylidenemethylamine 1 (1.19 g) and acetylacetone 2a (1 g) was adsorbed onto montmorillonite K10 (5 g) and allowed to stand at room temperature for 3 days. The mixture was extracted with CH2C12, the clay separated by filtration and the solvent evaporated under reduced pressure. Pure compound 3 could be isolated by short-path distillation (81% yield). The equimolar mixture of enamino ketone 3 and alkene 4a (5 mmol) was allowed to stand at room temperature for a suitable time. Washing with suitable solvent afforded the pure solid product 5. 

Acetylacetone la (10 mmol), metliyl vinyl ketone 2a (10 mmol) and bismuth trichloride (0.32 g, 10% mol) were mixed together without solvent in an Erlen-meyer flask and placed in a commercial microwave oven (operating at 2450 MHz frequency) and irradiated for 15 min. The reaction mixture was allowed to reach room temperature and extracted with chloroform. Removal of solvent and the residue on purification by passing through a short column of silica gel using chloroform as eluent, affords the Michael adduct 4a in 90% yield without tlie formation of any side products. Similarly cadmium iodide (10% mol) was used in place of bismuth trichloride and the corresponding Michael adduct was isolated in 85% yields. 

Group IIB. As, Sb, and Sn The separation of a mixture of the three elements is a difficult operation. The metals are present as their lower chlorides in dilute (2-4m) hydrochloric acid. The solution is spotted on paper and allowed to dry in air for 15 minutes. The solvent consists of 7-5 ml acetylacetone (b.p. 137°-141°) saturated with water and treated with 0 05 ml concentrated hydrochloric acid and 2-5 ml acetone (sufficient of the last-named to give a clear solution). The separation is allowed to proceed for 1 hour in an atmosphere saturated with respect to a saturated solution of acetylacetone in water the solvent movement is about 15 cm. The complexes formed are very stable, particularly that with tin (Rf = 1). The strip is removed from the extraction vessel, the solvent is allowed to evaporate for several minutes, and the strip is sprayed (before it is completely dry) with a chloroform solution of dithizone (0-005 per cent w/v), and then allowed to dry thoroughly. The tin is found in the solvent front. 

At the end of polymerization the mixture was treated with an additional 100 ml of cyclohexane solvent to fluidify the medium, 1 ml of 1M acetylacetone in cyclohexane added to stop the reaction, and A-l,3-dimethylbutyl-A -phenyl-p-phenylenediamine (0.02 g) added as an antioxidant. Polyisoprene was then extracted by steam stripping for 30 minutes in the presence of calcium tamolate. Each extraction was then dried for approximately 18 hours in an oven at 50°C under 200 mmHg vacuum for 72 hours. Reaction scoping results are provided in Table 1. 

An = Th, U, Np, and Pu. In complexing with metal ions, the / -diketones form planar six-member chelate rings with elimination of the enol proton. The simpler / -diketones, such as acetylacetone (HAA), are fairly water soluble, but form complexes that may be soluble in organic solvents. This is especially true for the An ions which form strong complexes with HAA and can be effectively sequestered to the organic phase, making HAA a potentially useful extractant (See Table 27). The four stability constants in Table 27 for tetravalent actinides imply that four HAA ligands coordinate with each metal ion in the formation of the extracted neutral ML4 complexes. ... 

The solvent properties of alcohols with short carbon chains are similar to those of water and such alcohols could be used as the nonaqueous catalyst phase when the products are apolar in nature. The first commercial biphasic process, the Shell Higher Olefin Process (SHOP) developed by Keim et al. [4], is nonaqueous and uses butanediol as the catalyst phase and a nickel catalyst modified with a diol-soluble phosphine, R2PCH2COOH. While ethylene is highly soluble in butanediol, the higher olefins phase-separate from the catalyst phase (cf. Section 2.3.1.3). The dimerization of butadiene to 1,3,7-octatriene was studied using triphenylphosphine-modified palladium catalyst in acetonitrile/hexafluoro-2-phe-nyl-2-propanol solvent mixtures [5]. The reaction of butadiene with phthalic acid to give octyl phthalate can be catalyzed by a nonaqueous catalyst formed in-situ from Pd(acac)2 (acac, acetylacetonate) and P(0CeH40CH3)3 in dimethyl sulfoxide (DMSO). In both systems the products are extracted from the catalyst phase by isooctane, which is separated from the final products by distillation [5]. 

The extraction of chelates is usually applied to preconcentration and separation of small amounts of metals. Owing to their low solubility in organic solvents, most chelates can not be used for the extraction of macrocomponents. Cupferronates and acetylacetonates are exceptions. 

Only those organic reagents, such as cupferron and acetylacetone, which form chelates highly soluble in non-polar organic solvents, can be used in the extraction of matrix elements. 

---