Solvent extraction with isopropylether

In aqueous solution, astatine is usually found in the free (0) state. However, unlike the other halogens, astatine(O) is not diatomic. It can be volatilized from solution and extracted (like iodine) into organic solvents such as benzene and carbon tetrachloride. Coextraction with halogens, X2, into chloroform produces interhalogen compounds, AtX (X = Cl, Br, I). Reaction with halide ion, X , yields polyhalide ions, AtX2 (X = Br, I) and AtIBr , which can be extracted into isopropylether. 

After extraction into hexane, a solid-phase extraction, using silica and nonpolar eluents, or sometimes reversed-phase extraction with polar solvents, is common in many assays. Some research groups used a semipreparative HPLC method (silica column and acetonitrile [62,67,68] or di-isopropylether [89] in hexane) with UV detection for cleanup. Blanco-Gomis et al. (60,61), introducing narrow-bore HPLC or capillary liquid chromatography for small-sample analysis of vitamins, were able to get appropriate results without solid-phase cleanup by reextracting the hexane layer with methanol water 9 1 to remove interfering lipids, as described elsewhere (24,88,108). 

To a solution of 4.76 g of 1-(4 -methyl-6 -methoxy-2 -pyrimidinyl)-3-methyl-3-pyrazoline-5-one in 200 ml of ether was added an ether solution containing 6 molar equivalents of diazomethane and the reaction mixture was allowed to stand at room temperature for 20 hours. After distilling off the solvent, the residue was dissolved in 160 ml of water, made alkaline (pH 10) with sodium hydroxide solution and extracted three times with 140 ml of benzene. The extract was washed with a small amount of water, dried over sodium sulfate and evaporated to give a crystalline mass. Recrystallization from isopropylether gave 1-(4 -methyl-6 -methoxy-2 -pyrimidinyl)-3-methyl-5-methoxypyrazole (3.96 g, 84%) as colorless prisms, MP 90° to 92°C. 

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See also in sourсe #XX -- [ ]

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