Ethyl acetate, purification

It is important to use dry ethyl acetate, but it should contain 2-3 per cent, of alcohol. The so-called absolute or anhydrous ethyl acetate of commerce is satisfactory. Experimental details for the purification of 95-97 p>er cent, ethyl acetate are given in Section 11,47,29. 

Although this process has not been commercialized, Daicel operated a 12,000-t/yr propylene oxide plant based on a peracetic acid [79-21-0] process during the 1970s. The Daicel process involved metal ion-catalyzed air oxidation of acetaldehyde in ethyl acetate solvent resulting in a 30% peracetic acid solution in ethyl acetate. Epoxidation of propylene followed by purification gives propylene oxide and acetic acid as products (197). As of this writing (ca 1995), this process is not in operation. 

Adipic acid [124-04-9] M 146.1, m 154 , pK 4.44, pK 5.45. For use as a volumetric standard, adipic acid was crystd once from hot water with the addition of a little animal charcoal, dried at 120 for 2h, then recrystd from acetone and again dried at 120 for 2h. Other purification procedures include crystn from ethyl acetate and from acetone/petroleum ether, fusion followed by filtration and crystn from the melt, and preliminary distn under vac. 

Cholesterol [57-88-5] M 386.7, m 148.9-149.4 , [a]D -35 (hexane). Crystd from ethyl acetate, EtOH or isopropyl ether/MeOH. [Hiromitsu and Kevan J Am Chem Soc 109 4501 I987. For extensive details of purification through the dibromide, see Fieser [J Am Chem SoclS 5421 1953] and Schwenk and Werthessen [Arch Biochem Biophys 40 334 7952], and by repeated crystn from acetic acid, see Fieser [J Am Chem Soc 75 4395 1953]. 

P-Hydroxy-A-norpregn-3(5)-en-2-one (7) A solution of the hydroxy-methylene steroid (5) (24.8 g) dissolved in 240 ml of acetic acid and 240 ml of ethyl acetate is ozonized at — 10° with one molar equivalent of ozone. The resulting solution is diluted with 240 ml. of water and 60 ml of 30 % hydrogen peroxide and allowed to stand overnight. The solution is diluted with 1.5 liters of water and extracted with 3 x 700 ml portions of ethyl acetate. The combined extracts are washed with water, saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness under vacuum, leaving 23.4 g of a colorless amorphous residue of crude diacid. This material shows a maximum in the ultraviolet spectrum at 224 mp (s 6,400) indicating a 53 % yield of unsaturated acid (6). It is used without further purification. 

Flash chromatography is widely employed for the purification of crude products obtained by synthesis at a research laboratory scale (several grams) or isolated as extracts from natural products or fermentations. The solid support is based on silica gel, and the mobile phase is usually a mixture of a hydrocarbon, such as hexane or heptane, with an organic modifier, e.g. ethyl acetate, driven by low pressure air. (Recently the comparison of flash chromatography with countercurrent chromatography (CCC), a technique particularly adapted to preparative purposes, has been studied for the separation of nonchiral compounds [90].)... 

Extraction and purification of luciferin and luciferase (Viviani etal., 2002a) To isolate luciferin, the lanterns of the Australian A. flava were homogenized in hot 0.1 M citrate buffer, pH 5, and the mixture was heated to 95°C for 5 min. The mixture was acidified to pH 2.5-3.0 with HCl, and luciferin was extracted with ethyl acetate. Upon thin-layer chromatography (ethanol-ethyl acetate-water, 5 3 2 or 3 5 2), the active fraction of luciferin was fluorescent in purple (emission Lav 415 nm when excited at 290 nm). To isolate the luciferase, the cold-water extract prepared according to Wood (1993 see above) was chromatographed on a column of Sephacryl S-300. On the same... 

Extraction and purification (Shimomura, 1989). Fruiting bodies are extracted with 30% methanol, and the extract is concentrated under reduced pressure. The residual solution (pH 6.0) is first washed with ethyl acetate, then acidified to pH 2.0 with 1 M HC1 and extracted with ethyl acetate. The extract is evaporated nearly to dryness. The residue is dissolved in 30% methanol and purified by the following 3-step procedure. 

Extraction and purification (Shimomura, 1991b). The luciferin precursors PS-A and PS-B are extracted from the dried fruiting bodies of Panellus stipticus (5 g) with methanol, and the extract is evaporated under reduced pressure to remove most of the methanol. The residue (pH 6.3) is diluted with a small amount of water and extracted with ethyl acetate, and the extract is evaporated to dryness. The precursors in the residue are purified by three steps of silica gel chromatography and one step of HPLC, while monitoring the absorbance of eluate at 220-230 nm. The procedure is summarized below ... 

A solution of 4.5 g (19.9 mmol) 4-(fm-butyldimethylsilyloxy)-2-cyclohexenone and 452 mg (1 mmol) of mercury(II) iodide is stirred at r.t. for 15 min and then cooled to — 78 °C. 5.03 g (24.8 mmol) of 1-ethoxy-1-(tm-bulyl(iimethylsilyloxy)ethene are added dropwise during 15 min. The mixture is stirred at — 78 °C for 2 h, quenched with 302 mg (3 mmol) of triethylamine and allowed to warm to r.t. The mixture is filtered through a short (3 cm) column of silica gel (deactivated with a 5% triethylamine solution in hexane/ethyl acetate, 10 1) eluting with hexane/ethyl acetate (10 1) and concentrated in vacuo. Purification of the crude material by flash chromatography (silica gel, hcxanc/cthyl acetate 30 1) gave the adduct as a colorless oil yield 7.98 g (18.7 mmol, 94%) d.r. (cisjtrans) 95.2 4.8. 

The submitters purified the product by the following procedure. The residual pale yellow solid is dissolved in 50 ml of diethyl ether and the remaining solid is filtered off (Note 16). The filtrate is concentrated to a volume of ca. 25 mL, and the solution is allowed to crystallize at 0°C. Once crystallization begins, 50 mL of petroleum ether is added in two portions over 10 hr, and then crystallization is allowed to proceed overnight at 0°C. The white solid is collected by filtration and washed with a mixture of 3 1 petroleum ether-diethyl ether to afford 3.8 g of 4. Chromatographic purification of the mother liquor (5.5 x 18 cm of DSH silica gel 40-63 mm, elution with 1 L of petroleum ether/ethyl acetate 4 1 followed by 1.5 L of 3 1 petroleum ether-ethyl acetate) gives 2.5 g of 4 as a pale yellow solid. All the material is combined and recrystallized from diethyl ether/petrol as above to yield 5.2 g (47%) of 4 in two crops. 

Preparation by fermentation of Saccharomyces cerevisiae (baker yeast) with addition of L- or DL-methionine, lyse of cells with ethyl acetate and purification by ion-exchange chromatography. 

After extraction, an extract purification stage is generally reconunended. This is most often done by liquid-solid exchange using resins such as Sephadex, Amber-lite XAD-7, or Cjg mini-columns. ° All the polar compounds are first trapped on the resin, and then in succession the sugars, acids, and other polar compounds (excluding polyphenolic compounds), polyphenolic compounds (excluding anthocyanidins), and anthocyanidins are respectively eluted with acidified water (HCl 0.01% v/v), ethyl acetate, and acidified methanol (HCl 0.01% v/v). 

The use of ethyl acetate was suggested by Oszmianski and Lee (1990) to wash out phenolics other than anthocyanins. Finally, a relatively pure anthocyanin extract can be removed from the colnmn with acidified methanol (0.1% HCl). Anthocyanin extracts can be enriched in this way by use of solid phase purification, which is especially helpful for diluted samples such as biological samples. Two factors in the nse of these purification techniques are the stability of anthocyanins to the conditions nsed and the ease of anthocyanin recovery from the column. ... 

For example, an alumina layer with a nonaqueons mobile phase was optimized for the separation of the taxoid fraction from ballast snbstances [5]. Figure 11.3 shows the densitogram obtained for Taxus baccata cmde extract chromatographed on the alnmina layer developed with nonaqueous elnents. The nse of ethyl acetate and dichloromethane enables elntion of nonpolar fractions (chlorophylls and waxes) and purification of the starting zone (Figure 11.3a). In this system, all taxoids are strongly retained on the alumina layer. The use of a more polar mobile phase... 

PLC separations (Figure 16.13) started with toluene-ethyl acetate (95 + 5 v/v) as the mobile phase, whereas the final purification was achieved with cyclohexane-diethyl ether (80 -i- 20 v/v). The isolated and extracted compound matched the GC-MS of 24-norursa-3,12-dien-ll-one (compound 11) and is confirmed as an oxidized pyrolyzed boswelhc add. 

In another study, catfish samples were homogenized in ethyl acetate, and the residues were partitioned into acetonitrile and petroleum ether, subjected to C-18 SPE purification, and analyzed using LC/UV detection. "" Quantitative recoveries were obtained for atrazine, simazine, and propazine in the 12.5-100 lagkg concentration range. 

The crude product is dissolved in a minimum amount of dichloromethane and adsorbed onto 25 g of silica gel (32-63 micron) by subsequent evaporation of the dichloromethane under reduced pressure. The sample of dry, dark brown silica gel is added to the top of a column containing 500 g of silica gel (32-63 micron) with a mobile phase of hexanes. The polarity of the mobile phase is gradually increased from hexanes to 95 5 hexanes-ethyl acetate. The fractions containing the desired product (Rf = 0.26, 95 5 hexanes-ethyl acetate) are combined and concentrated under reduced pressure to yield 6.9 g of 3 as a yellow solid. Additional purification is required to remove traces of tin by-products. Compound 3 is dissolved in 70 mL of... 

Both ethyl acetate and hexanes were obtained from Fisher Scientific Company and used without further purification. 

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