Column chromatography, on alumina

Method A A solution of the azidoquinoline (5 mmol) in 3M KOMe in MeOH (40 mL) and dioxane (40 mL) was irradiated under N2 using a water-cooled, 125-W medium-pressure Hg lamp until all the azide [as measured by the disappearance of u(N3) at 2120 cm" 1 or by TLC] had reacted (4-10h). The photolysate was left to stand at 20 C for 24h then neutralized cautiously by the addition of 4M IICI in MeOH. The solvent was removed under reduced pressure and the crude product was purified initially by column chromatography on alumina (Type H, toluene), then finally by crystallization (petroleum ether). 

This material should be at least 98% pure by vapor-phase chromatography (SE-30 column at 180-200°). It usually crystallizes if stored in a refrigerator. Unreacted hexamethylbenzene, present if insufficient oxidant is used, can best be removed by column chromatography on alumina with pentane as eluant. 

Recently, Mascal and Ceron Bertran <2005JA1352> reported the preparation and characterization of 35 (aza-analogue anions of triquinacenes) which are stable enough in THF solution (in the absence of acid). Moreover, the hexachloro anion 35b could be isolated as tetraethylammonium salt by column chromatography on alumina. As expected, anion 35a was more nucleophilic than 35b. Indeed, only the former could be benzylated leading to 36a. However, 35b reacts easily with molecular bromine at low temperature yielding the corresponding a,a,a-tribromide 37b or dibrominated ether 37 b when this bromination was conducted in THF. 

Checkers used column chromatography on alumina and observed 5% anti isomer eluting first. 

This method involves acid hydrolysis of the urine followed by extraction with toluene, oxidative purification with permanganate, adsorption chromatography, acetylation, column chromatography on alumina, and finally quantification by colorimetric determination of the sulfuric acid chromogen. It is now generally accepted that this method is not as sensitive or as specific as the newer methods of GC. 

Metobromuron Plant leaves Column chromatography on alumina and spectrophotometry of azo derivatives [156]... 

Scheme 11 shows the standard route to lanthanide porphyrin complexes [24,235,236], Depending on the lanthanide metal all intermediates and products can be isolated via column chromatography on alumina. 

All quaternization reactions were performed under the same conditions, e.g., in ca. 0.08 M solution in acetone, at ambient temperature, for 20 h, and a pressure of 10 kbar was maintained during the reaction course. Without exception colourless crystalline solids precipitate in the reaction cell, and after a simple work-up (washing with hexane and drying in vaccuo) the isolated bisquaternary salts were analytically pure. Demethylation was carried out by heating the respective salt with triphenyl-phosphine in boiling DMF, followed by column chromatography on alumina. Yields obtained for the quaternization and demethylation reactions are listed in Table 2. 

The most commonly used methods for isolation and purification of phospholes are crystallization, generally performed at low temperature, and column chromatography on alumina or silica gel. A wide variety of solvents have been used as eluents, including protic solvents such as methanol. 

Direct alkylation of 5-substituted tetrazoles is often the best method of obtaining simple 2,5-disubstituted tetrazoles. The 1,5-isomers, which are formed as competitive side products, are usually separated with ease by fractional crystallization or better by column chromatography on alumina or silica gel which gives excellent separations of most tetrazole isomers (8UCR(S)174). Another convenient synthesis of 2,5-disubstituted tetrazoles (241) is the formazan method (Scheme 31). By coupling aldehyde arylsulfonylhydrazones (240) with diazonium salts in basic solutions, compounds (241) may be obtained directly in yields of up to 78% (76BCJ1920). 

The first synthesis of molecules of this kind was reported independently by Vogtle [52] and Hall [51] and both involved condensation of 34 with a range of diazamacrocycles 37 under high dilution conditions to form the corresponding amide cryptands 38 together with dimeric analogues 39 and some polymers. The compounds were easily separated by column chromatography on alumina and were fully characterised by mass spectrometry, elemental analysis, and multinuclear NMR... 

Pd2(dba)3 CHCl3 (52 mg, 0.1 mmol) and dppe (80 mg, 0.2 mmol) were placed in a 30mL two-necked flask which was flushed with argon. THF (2mL) was added to dissolve the catalyst. Then a solution of carbonate 176 (228 mg, 2 mmol) and methyl acetoacetate 183 (232 mg, 2 mmol) in THF (3mL) was added, and the mixture was stirred at room temperature for 4h. The resultant mixture was filtered through Florisil. The furan 186 (272 mg, 88%) was isolated by column chromatography on alumina. 

We report on the further physical and chemical characterization of the new forms of molecular carbon, C ) and C70. Our results demonstrate a high yield of production (14%) under optimized conditions and reveal only and C70 in measurable quantity, in an 8S IS ratio. These two new molecular forms of carbon can be completely separated in analytical amounts by column chromatography on alumina. Comparison among mass spectra obtained by the electron impact, laser desorption, and fast atom bombardment (FAB) methods allows a clear assessment of the composition of the mixed and pure samples, and of the fragmentation and double ionization patterns of the molecules. In addition, spectroscopic analyses are reported for the crude mixture by C NMR and by IR spectroscopy in KBr pellet, and for pure C o and C70 in solution by UV-vis spectroscopy. 

The new molecular forms of carbon, C > and C70, were prepared following the method of KrStschmer et al. in a consistently high yield (14%). The benzene-soluble material extracted from the graphite evaporation product is predominantly constituted of C(o and C70. Three independent methods, namely HPLC, mass spectroscopy, and C NMR, demonstrate that these two compounds are present in a ratio near 85 15. The two compounds can be separated by column chromatography on alumina, allowing as for now the purification of minute quantities of pure and C70. Support for the proposed symmetrical cage structures (fullerenes) of C o and C70 is inferred from the simplicity of the C NMR spectra and the strong presence of the and ions. Attempts at the X-ray determination of the Cjo molecular structure are now actively pursued. ... 

In normal preparations the (4) formed is usually not isolated. The end of the condensation step is announced by the cleavage of nearly the theoretical amount of amine. The temperature of the mixture is then raised until a new evolution of di-methylamine sets in. During the thermolysis the color of (4) slowly fades and the second equivalent of amine is split off. Finally, the frequently dark reaction solution is worked up in a usual manner, e.g., by distilling off the quinoline in vacuo, or by dissolving the quinoline in dilute mineral acid when it is a small-scale preparation or when the product is too volatile for a separation by distillation. Further purification can be achieved by sublimation, crystalization, and column chromatography on alumina or silica gel. 

The products were isolated and purified by column chromatography on alumina grade III, then distilled (high vacuum) at rt all pure materials must be stored under argon below -25°C. 

Styrene monomer (Monsanto Aust Limited), DVB and TMPTA (Polysciences) were purified immediately prior to irradiation by column chromatography on alumina. 

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