Column chromatography results from

The versatility of column chromatography results from the many factors that can be adjusted. These include... 

Oligomerization of 1-butene oxide was studied for the reaction of a ninefold excess of 1-butene oxide with PSLi over the normal 2 days reaction time at room temperature in benzene. Analysis by both NMR and MALDI-TOF MS showed no evidence for oligomerization. MALDI-TOF MS did show a series of peaks corresponding to nonfunctiona-lized polymer (PS-H) present in the resulting product mixture as expected from the column chromatography results. 

The labeled acyl-ACPs were also recovered from the chloroplasts by silicic acid column chromatography modified from the silica gel thin-layer chromatography of Jackowski and Rock (1981) The incubation was stopped by adding 5 volumes of 1-butanol/acetic acid (4 1, v/v), and the resultant... 

Three general methods exist for the resolution of enantiomers by Hquid chromatography (qv) (47,48). Conversion of the enantiomers to diastereomers and subsequent column chromatography on an achiral stationary phase with an achiral eluant represents a classical method of resolution (49). Diastereomeric derivatization is problematic in that conversion back to the desired enantiomers can result in partial racemization. For example, (lR,23, 5R)-menthol (R)-mandelate (31) is readily separated from its diastereomer but ester hydrolysis under numerous reaction conditions produces (R)-(-)-mandehc acid (32) which is contaminated with (3)-(+)-mandehc acid (33). 

There are a number of causes of peak asymmetry in both gas and liquid chromatography, including heat of adsorption, high activity sites on the support or absorbent, and nonlinear adsorption isotherms. Assuming that good quality supports and adsorbents are used, and the column is well thermostatted, the major factor causing peak asymmetry appears to result from nonlinear adsorption isotherms. 

So far the plate theory has been used to examine first-order effects in chromatography. However, it can also be used in a number of other interesting ways to investigate second-order effects in both the chromatographic system itself and in ancillary apparatus such as the detector. The plate theory will now be used to examine the temperature effects that result from solute distribution between two phases. This theoretical treatment not only provides information on the thermal effects that occur in a column per se, but also gives further examples of the use of the plate theory to examine dynamic distribution systems and the different ways that it can be employed. 

Column Chromatography Column Chromatography is a useful separation technique for mixtures resulting from intermediate to small scale synthetic processes. For example, nitroferrocene is conveniently isolated from a mixture of the product, ferrocene, and l,r-dinitroferrocene by chromatography on Activity I basic alumina at about the 100-g scale (Chapter 7, Section XI). 

Removal of solvent from the extracts leaves a residue that is purified by dry-column chromatography.2 The residue is dissolved in 40 ml. of acetone in a 300-ml., round-bottomed flask, 30 g. of silica gel (Note 8) is added, and the acetone is removed with a rotary evaporator. The resulting solid mixture is placed on top of 360 g. of dry silica gel (Note 8) packed in flexible nylon tubing (Note 9), and the column is developed with 420 ml. of 10 1 (vjv) benzene-acetone. Approximately 150 ml. of solvent drips from the bottom of the column toward the end of development, and this eluent is collected in 25-ml. fractions and checked for product by thin layer chromatography (Note 10). The column itself is then cut into 2-cm. sections, the silica gel in each section is eluted with three 25-ml. portions of ethyl acetate, and the eluent from each section is analyzed by thin-layer chromatography (Note 10). Combination of all the product-containing fractions yields 1.2-1.5g. (40-47%) of the benzylated compound as an oil, n 1.6083 (Notes 11 and 12). 

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