Eluent, sodium thiosulfate

An ethanediyl 5,5-acetal (lmmol) was added to a solution of t-butyl bromide (3.05 g) and DMSO (1.5 g). The mixture was heated to 70-75°C under a nitrogen atmosphere. The reaction was followed by thin layer chromatography (silica gel/hexane) and GLC (capillary OV-101 column). Upon completion of the reaction the mixture was poured into water (15 ml) and extracted with hexane (3 X 20 ml). The combined hexane extracts were washed successively with aqueous sodium thiosulfate (10 ml) and water (2 X 10 ml), dried with anhydrous sodium sulfate, and the solvent evaporated. The residue was purified by column chromatography on silica gel using hexane as an eluent, followed by distillation or crystallization to give the corresponding carbonyl compound. 

A mixture of benzaldehyde (1.06 g, 10 mmol), ethane-1,2-diol (0.62 g, 10 mmol) and commercial grade cadmium iodide (1.85 g, 5 mmol) were thoroughly mixed at room temperature in an Erlenmeyer flask and placed in a commercial micro-wave oven operating at 2450 MHz frequency. After irradiation of the mixture for 1.5 min (monitored vide TLC) it was cooled to room temperature, extracted with dichloromethane, washed with sodium thiosulfate and dried over anhydrous Na2S04- Evaporation of the solvent gave almost pure products and there was no evidence for the formation of any hydroxy ester or iodoester. Further purification was achieved by column chromatography on silica gel using 1 5 chloroform-petroleum ether as eluent. 

To a mixture of glucopyranose (0.22 mmol) in dry cyclohexane (24 ml) under an argon atmosphere were added iodosylbenzene (0.43 mmol) and iodine (0.22 mmol) at room temperature. The mixture was stirred for 20 h at the same temperature. After the reaction, the reaction mixture was poured into water and extracted with ether. The organic layer was washed with aq. sodium thiosulfate solution, water, and dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel (eluent hexane/ethyl acetate = 65/35) to give D-arabinose derivative in 86% yield [68]. 

Representative procedure. To a solution of Sml2 in THF (2.2 mmol) at —78 °C was added a mixture of the aldehyde (1.0 mmol) and acylated oxazolidinone (1.0 mmol) in THF dropwise over 5 min. The resulting solution was then stirred at —78°C for 30 min, during which time the reaction mixture decolourised. The solution was then quenched with 0.1 M HC1 and the aqueous layer extracted with Et20. The organic layers were washed with sodium thiosulfate and brine, dried (MgS04) and concentrated in vacuo. The crude product was purified by preparative TLC (ethyl acetate-hexane as eluent). 

Stirring over 10 min. The solution immediately turned brown and was then stirred at room temperature for 2 h. The carbon disulfide was removed under reduced pressure, and the residue was extracted with ether. The ether extract was washed successively with sodium hydroxide (2 N) solution, 12% sodium thiosulfate solution, 1.5 sulfuric acid, water, saturated sodium bicarbonate solution, and saturated sodium chloride solution. The extract was dried over MgS04 and evaporated. The resulting brown residue (1.8 g) was chromatographed on 200 g silicic acid-Supercel using pentane as the eluent, to afford 1.48 g 1,2-diethynylcyclohexene as a colorless liquid, in a yield of 19%, b.p. 52-53°C (18 mmHg, under nitrogen). 

Dicarbonyl(cyclopentadienyl)iron dimer (10.0 g, 28 mmol), chloroform (150 mL), and iodine (8.6 g, 34 mmol) are sequentially added in a 300-mL round-bottomed flask under air. After the mixture is filled with argon, it is refluxed and stirred for 2 h. Then, the resulting mixture is cooled to room temperature and quenched with an aqueous solution of sodium thiosulfate. The products are extracted with chloroform (3 x 100 mL), and the combined organic layer is dried over sodium sulfate and concentrated. Silica gel column purification (eluent chloroform) of the crude product provides dicarbonyl(cyclopenta-... 

The eluent was 0.1 M sodium acetate buffered to pH 6 in 70% methanol 30% water. The procedure was run in the isocratic mode at 1.0 mL/min with a nominal pressure of 700-800 psi. The applied potential to the working electrode was 0 V versus the Ag-AgCl reference electrode. Chloride and bromide did not interfere with the determination of thiosulfate and iodide because they are weakly electroactive at the applied potential. Retention times in minutes are 2.0 (Cl ), 3.9 (Br"), 8.4 (T), and 12.5 (S2 032 ). 

A silver wire electrode coated with AgCl has excellent selectivity. An ion chromatogram obtained with 4.5 mM sodium perchlorate as the eluent gave sharp peaks for 1 mM chloride, bromide, iodide, thiocyanate and thiosulfate but no response to equi-... 

With direct spectral detection, the detector is set at a wavelength where the sample anions absorb but the eluent cation and anion do not. A number of inorganic anions including nitrate, bromide, iodide, thiocyanate, bromate and thiosulfate, as well as aromatic organic anions, can be detected. Sodium chloride, sodium perchlorate, or a number of other anions could be used in the eluent... 

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