Silica columns chromatographic separations

Condensation of o-aminoacetophenone with maleic, succinic or phthalic anhydrides gave 117 whose bromination with CuBr2 gave the bromides 118. Column chromatographic separation of the respective maleimide derivative on silica gel gave the bromoquinoline 119 whereas the phthalimide derivative was obtained from 118 by cyclization with EtsN (93MI11). On the... 

The submitters mixed active anhydrous silica gel with water (12% v>/w) and stored it in a sealed container for at least 24 hours prior to use. A ratio of 60-80 g. of silica gel per gram of crude product was used for column chromatographic separations, and a column was chosen that would give a 10 1 height diameter ratio of adsorbent. Columns were wet-packed with distilled petroleum ether (b.p. 60-68c), and after the crude product had been applied a step-gradient was run rapidly through 2% vjv ether in petroleum ether, 5% ether, and 10% ether. The column was then eluted with 20% vjv ether in petroleum ether until the bromohydrin acetate was obtained. 

A solution of (3) (215mg, 0.799mmol) in methanol (10ml) was refluxed for 13 h in the presence of two drops of triethylamine. After column chromatographic separation (silica gel, dichloromethane), crude methyl ester (4) (192 mg, 0.759 mmol) was obtained, m.p. 166-167°C (recrystallization from dichloromethane/carbon tetrachloride/n-hexane and water/methanol). Crude (4) thus obtained was treated with... 

Photolysis of 1.00 g (3.90 mmol) of 9-diazothioxanthene-5,5-dioxidel l in 20 mL of p-methylstyrene, contained in 25 mL-size Vycor glass, using a Hanovia lamp (450 W), was continued until disappearance of the starting diazo-red color. After vacuum distillation of the unreacted styrene, column chromatographic separation of the residue (silica gel, methylene chloride/n-pentane (1 2)), solvent removal and recrystallization from ether afforded 1.10 g (81%) of 2.10b, mp 190 °C. 

For resorcinolic lipids, particularly those with long saturated side-chains, the use of polar solvents is important due to their amphiphilicity. The crude extracts in many cases are subjected to preliminary fractionation/purification either by solvent fractionation/partition or by application of chromatography. For prepurification of the material and its separation from polymerized phenolics, gel filtration on hydrophobic Sephadex or TSK gel is sometimes used. Silica gel is most frequently employed for the separation and/or purification of resorcinolic lipids, notably in some studies with Ononis species (12-14). The array of compounds reported appears partly attributable to methylation or acetylation reactions occurring during column chromatographic separation. An interesting approach for I the pre-purification and selective separation of resorcinolic lipid from phenolic lipids or resorcinolic lipids from impurities has recently been reported. A selective partitioning of different non-isoprenoid phenolic lipids... 

Alkaloids of Atragene sibiriaa L. - Chloroform extraction of the roots of this species (Siberian clematis Ranunculaceae) followed by isolation of the bases and column chromatographic separations with silica and alumina afforded five alkaloids.Two of these were identified as delphinine (101) and aconitine (14) from their physicochemical and i.r. spectral data and by direct comparisons. 

A number of attempts to extend the usual temperature range of capillary columns in order to elute PAH above coronene have been successful. Grob (25) was able to chromatograph stable PAH-compounds from coronene up to rubrene (molecular weight 300 to 532) on a short DV-lDl column. Romanowski et al. (26) used a 15 meter SE-54 fused silica column to separate PAH in the molecular weight range from 300 up to 402, in combination with FID and MS detection. A recent review on the performance of capillary columns in PAH-analysis has been published by Lee and Wright (27). 

Residues obtained from the filtrates of multiple recrystallizations of 6A were combined to give a gummy solid. This was subjected to column chromatographic separation on silica gel with chloroform and ethanol as successive eluants. 

Residues obtained from filtrates of multiple recrystallizations of 6B were combined and subjected to column chromatographic separation with silica gel as adsorbent and chloroform and ethanol, respectively, as eluants. Residual quantities of 6B separated out in the first fraction followed by a compound showing the presence of both carbonyl and nitro absorption frequencies in the IR spectrum. This was followed by 8B (0.5%) in the pure form. The mixture of isomers had m.p. 155-60°C. Anal. Calcd. for C12H20N2O3 C, 60.00 H, 8.33 N, 11.66. Found C, 60.08 H, 8.57 N, 11.45. u max cm i 3300-... 

The method below is based on hydrolysis of sulfate groups, followed by column chromatographic separation of derivatives of the resulting alcohols and alcohol ethoxylates. Only the unethoxylated material elutes from a silica gel column. 

It is clear that the separation ratio is simply the ratio of the distribution coefficients of the two solutes, which only depend on the operating temperature and the nature of the two phases. More importantly, they are independent of the mobile phase flow rate and the phase ratio of the column. This means, for example, that the same separation ratios will be obtained for two solutes chromatographed on either a packed column or a capillary column, providing the temperature is the same and the same phase system is employed. This does, however, assume that there are no exclusion effects from the support or stationary phase. If the support or stationary phase is porous, as, for example, silica gel or silica gel based materials, and a pair of solutes differ in size, then the stationary phase available to one solute may not be available to the other. In which case, unless both stationary phases have exactly the same pore distribution, if separated on another column, the separation ratios may not be the same, even if the same phase system and temperature are employed. This will become more evident when the measurement of dead volume is discussed and the importance of pore distribution is considered. 

Further members of this class of alkaloids are the araguspongines K (10) and L (11), isolated from the marine sponge Xestospongia exigua collected at Bayadha, on the Saudi Arabian Red Sea coast [16]. After evaporation of the EtOH extract, it was partitioned between hexanes and MeCN. The polar fraction was subjected to a series of chromatographic separations by column chromatography on silica gel. The structures of both alkaloids 10 and... 

In order to reduce the time-consuming open-column chromatographic processes, conventional methods of hydrocarbon-group-type separation have been replaced by MPLC and HPLC. Flash column chromatography is a technique less commonly applied than open-column version, but several applications have been described [2,24—27]. The common technique version is to use a silica-gel-filled column for example, 230 to 400 mesh 20 X 1 cm column size with a back pressure of 1.5 X 10 Pa of an ambient gas such as nitrogen. Solvents are similar to the ones apphed in the case of open-column chromatography fractionations. 

Monde, T., Kamiusuki, T., Kuroda, T., Mikumo, K., Ohkawa, T., and Fukube, H., High-performance liquid chromatographic separation of phenols on a fluorocarbon-bonded silica gel column, /. Chromatogr. A, 722, 273, 1996. 

Preparation of 6 -[4-(4-Anilinoanilino)anilino]-2 -chloro-3 -methylflu-oran (81a). To concentrated sulfuric acid (10 g) was added 2-(5-chloro-2-hydroxy-4-methylbenzoyl)benzoic acid (3.4 mmol) followed by 4-anilino-4 -(3-methoxyanilino)diphenylamine (2.6 mmol). The mixture was stirred at room temperature for 24h, and poured into ice water (100ml). The precipitate was filtered off, washed with water, and then refluxed with a mixture of toluene (150 ml) and sodium hydroxide (20 g) dissolved in water (150ml) for 1 h. The toluene layer was separated, washed with hot water, and concentrated. The residue was then column chromatographed on silica gel to give 6 -[4-(4-anilinoanilino)anilino]-2 -chloro-3 -methylfluoran in 43% yield as a grayish white powder, mp 202-203 °C. 

When two monolithic silica columns were used for two sets of 2nd-D chromatographs (Fig. 7.6c) separating each fraction of the lst-D effluent alternately,... 

Tanaka, N., Kobayashi, H., Ishizuka, N., Minakuchi, H., Nakanishi, K., Hosoya, K., Ikegami, T. (2002). Monolithic silica columns for high-efficiency chromatographic separations. J. Chromatogr. A 965, 35-49. 

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