Flash chromatography column packing

You will now slurry pack a micro flash chromatography column. Place a small pipet bulb on a disposable pipet... 

Ai-aryl benzamide (1 0.20 mmol), [RuCl2(pcymene)]2 (0.02 mmol), 0-benzoyl hydroxylamine (2 0.60 mmol), and K2CO3 (0.40 mmol) dissolved in acetone (1 mL) was stirred in a 25 mL Schlenk tube at room temperature under argon atmosphere for 36 h. Upon completion, the reaction mixture was diluted with ethyl acetate and filtered through a small pad of Celite. The filtrate was concentrated in vacuo and purified by a silica gel packed flash chromatography column, using ethyl acetate/hexane as the eluent to furnish pure substituted aryl/heteroaryl amine 3. All the products were characterized by spectral methods. 

The product may also be purified by flash chromatography using 19/1 (v/v) petroleum ether, (bp 3Q-60 C)/ethyl acetate as eluant. A column of 2-cm diameter was packed to a height of 25 cm with Kieselgel 60 (230-400 mesh) supplied by BOH Chemicals Ltd. In one run chromatography of 4.19 g of crude product afforded 3.70 g (88%) of the a.g-unsaturated ester which was... 

Mother liquors from the production of bromocriptine 2 were dried by evaporation under vacuum. The dry residue (82.2 g) was applied on chromatographic column (I.D. = 3 cm, lenght = 20 cm) packed with silicagel 60, granulation 0.063 - 0.040 mm and eluted by flash - chromatography with pure dichloromethane. Two separate fractions were obtained and crystallized from dichloromethane (- 15°C). 

Dry-column flash chromatography. This technique has been developed from flash chromatography by L. M. Harwood.64 The principal feature is that suction is applied to the column packing, and eluting solvents are added in predetermined volumes with the column being allowed to run dry before the next fraction is added. Furthermore the apparatus is both simple and of easy operation. 

A column (350 mm x 50 mm) packed with Merck silica gel 60 (230-400 mesh ASTM) was used. Elution was facilitated by the action of an air pump for tropical fish tanks available from supermarkets. After use, the column was washed successively with methanol (500 mL), ethyl acetate (400 ml ), and hexane (400 mL). Such a washing operation reactivates the column enough for reuse to purify the epoxide (3), if necessary (see Note 15). Thus the submitters can employ the same column repeatedly for the purification of 2 and 3 (over 10 times). The checkers recommend purification by flash chromatography using a 350-mm x 50-mm column. 

Flash chromatography is a quick preparation technique that is, in effect, a hybrid between medium pressure and short column chromatography. It uses a short, fat column (e.g., 1-5 cm i.d. x 45 cm) packed with silica gel and filled with solvent. Compressed air is used to compress and remove the air from the solvent which then elutes quickly. The sample is then added and the column filled again. Pressure is adjusted to achieve a separation in 5-10 minutes. It is a fast and inexpensive method for the preparative separation of mixtures requiring only moderate resolution. Use of 40-63 pm sihca gel and a pressure driven flow rate of 2.0 in/min are essential for successful separation [30]. 

Column chromatography is typically the next step after determination of the polarity of the extract components. Nonpolar compounds are usually chromatographed on silica-gel stationary phases. Vacuum column chromatography (VCC) or vacuum flash chromatography can provide a fast and simple first separation of an extract. This can be followed by additional VCC or by HPLC. Both silica-gel and reverse phase packings can be used (29,30). 

Flash chromatography (FC) is a simple, low cost and rapid column chromatographic technique used principally for the separation and purification of mixtures of organic compounds (Chapter 9, Experiment 15). The technique, first described by Still [1] uses a smaller and narrower range particle size of packing than conventional preparative column chromatography and as such has to be carried out with a slightly increased over-pressure in order to achieve adequate flow-rates. 

Column packing 40-63, silica gel, Merck, Flash chromatography grade ex BDH. 

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