Solvent cyclohexane-ethyl acetate

Figure 6. Separation of neutral dansyl cannabinoids by one-dimensional TLC. Developing solvent cyclohexane/ethyl acetate (95 5). The striped spots indicate breakdown products of DANS-Cl. The left side of the plate shows the products of derivatization of standards. The right side shows a blank reaction mixture.

Fig. 93. Isolation by TLC of two steroids, tritiated by the WniZBACH method [617]. Layer silica gel G (0.9 mm thick) solvent cyclohexane-ethyl acetate (60 + 40) time of run 40 min amount 8 mg of the reaction mixture. The distribution of activity was measured directly on the layer with a counting tube. Zones showing activity were scraped off and eluted...

The most commonly used catalysts are palladized charcoal or calcium carbonate and platinum oxide. For better isotopic purity, the use of platinum oxide may be preferred for certain olefins since the substrate undergoes fewer side reactions while being chemisorbed on the platinum surface as compared to palladium.Suitable solvents are cyclohexane, ethyl acetate, tetrahydrofuran, dioxane or acetic acid-OD with platinum oxide. 

To a stirred solution of 1 g (3.48 mmol) of (3R,4R)-4-acetoxy-3-[(R)-l-(( Tt-butyldimethylsilyloxy)ethyl]-2-azetidinone in 20 mL of CH2C12 are added 1.46 g (5.17 mmol) of tetrakis(2-propeny])tin and 49.5 mg (0.348 mmol) of BF3 0(C2H5)2 under a nitrogen atmosphere. After stirring for 15 h at 20 °C, CH2C12 is added and the mixture is washed three times with water and then dried over MgS04. The solvent is removed in vacuo and the residue is purified by flash chromatography (cyclohexane/ethyl acetate 2 1) yield 800 mg (85%) nip 70-77 °C. 

Applications Open-column chromatography was used for polymer/additive analysis mainly in the 1950-1970 period (cf. Vimalasiri et al. [160]). Examples are the application of CC to styrene-butadiene copoly-mer/(additives, low-MW compounds) [530] and rubbers accelerators, antioxidants) [531]. Column chromatography of nine plasticisers in PVC with various elution solvents has been reported [44], as well as the separation of CHCI3 solvent extracts of PE/(BHT, Santonox R) on an alumina column [532]. Similarly, Santonox R and Ionol CP were easily separated using benzene and Topanol CA and dilaurylthiodipropionate using cyclohexane ethyl acetate (9 1 v/v) [533]. CC on neutral alumina has been used for the separation of antioxidants, accelerators and plasticisers in rubber extracts [534]. Column chromatography of polymer additives has been reviewed [160,375,376]. 

The crude product (10 g) is diluted with 4 mL of a solvent mixture (ethyl acetate/cyclohexane = 9 1). This solution is poured onto a column (75-mm diameter) filled with 120 g of silica gel (Merck 230-400 mesh) for flash chromatography. Elution is performed under gravity and requires 200 mL of the above solvent system, followed by 200 mL of ethyl acetate. 2-Phenyl-2-propanol mixed with methyl p-tolyl sulfide is eluted in the first fraction ( 150 mL, monitored by TLC). The subsequent fractions are collected ( 300 mL)... 

Into a solution of residue 59 (101 mg, 0.1 mmol) in 20 mL of dry toluene, kept at 60°C, was syringed, during 18 h and under argon, a freshly prepared solution of samarium diiodide in benzene-HMPA (9 1, v/v 6.3 mL, 0.51 mmol) which has been diluted with 3.8 mL of dry benzene. The solvents were distilled off under reduced pressure, and the residue was taken up in 10 mL of diethyl ether. The ether solution was washed with 10% aqueous solution of sodium bisulfite, then water, dried (MgS04), and concentrated. The crude product was dissolved in 1.5 mL of tetrahydrofuran and treated during 30 min at room temperature with 1.5 mL of a 40% aqueous solution of HF. The solution was neutralized with solid sodium carbonate, and concentrated. Flash chromatography on silica gel (cyclohexane-ethyl acetate, 3 1 to 1 2) afforded the product 80 (40.6 mg, 50%), a single isomer, as an amorphous solid. It was characterized by its diacetate [a]D +36° (c 4.0, CHClj). 

The product formed was extracted with CH2C12 (4x30 mL) and filtered on Celite. After evaporation of solvent, the product was purified by preparative thin layer chromatography (cyclohexane-ethyl acetate, 9 1) on silica and crystallized. 

Solvent systems A, chloroform-benzene-ethanol (18 2 1) B, chloroform-dioxane (47 3) C, cyclohexane-ethyl acetate (3 1). ... 

Solvents 1 = cyclohexane-ethyl acetate (1 1) 2 light petroleum-chloroform-diethyl ether-acetic acid (33 33 33 1) and 3 - heptane-ethyl acetate-butanol (8 1 1). 

Method. The derivatives are formed by shaking the sample (dissolved in acetone) for 1 h at 45 °C with a 3-5 molar excess of recrystallized DNS-C1. The reaction is buffered at pH 10.8.0.25 ml of 1N sodium hydroxide is then added in order to hydrolyze the unchanged DNS-C1. The derivatives are extracted with 3 ml of ethyl acetate after addition of 1 ml of a saturated aqueous solution of sodium chloride to the reaction mixture. The organic phase is used for TLC on activated layers of silica gel G. The cannabinoids yield mono-DNS derivatives with the exception of cannabidiol which forms a bis-DNS derivative. The following solvent systems are satisfactory for separation of cannabinoids on silica gel A, benzene-acetone (9 1) B, cyclohexane-ethyl acetate (5 1) C, cyclohexane-acetone-diethylamine (20 4 1) and D, cyclohexane-acetone-triethylamine (20 4 1). The R f values of nine cannabinoids in the above solvent systems are given in Table 4.25. 

R)-( + )-Pulegone 2 (2.0 g, 13.14 mmol) and ort/zo-phenylenediamine 1 (1.42 g, 13.14 mmol) were dissolved in 30 ml of dry toluene (Scheme A.31). Subsequently, the mixture was refluxed, the solvent evaporated and the residue subjected to column chromatography over silica gel (cyclohexane-ethyl acetate 7 3), producing 2.16 g (68%) of compound 3. Melting point 105°C. 

TLC was carried out on various types of plates silica gel, silanized silica gel, cellulose and alumina, as well as in several different solvent systems benzene, chloroform, cyclohexane, benzene/acetone (90 10), cyclohexane/ethyl acetate (95 5), cyclo-hexane/acetone/triethylamine (70 25 5), hexane/benzene (60 40) and hexane/ether (80 20). Spots were either visualized by ultraviolet or developed by pulverization of a 1% blue B salt aqueous solution. 

The best separation was obtained using the hexane/ benzene (60 40) and cyclohexane/ethyl acetate (95 5) systems. However the latter was the only system which produced a final satisfactory result as its background was 225 30 cpm compared to 705 53 for hexane/benzene. Two-dimensional TLC with two solvent systems -cyclohexane/ethyl acetate (95 5) for the first migration followed by hexane/benzene (60 40) for the second did not greatly improve the background, which was 291 34 cpm for the first development and 241 31 cpm for the second. 

A solution of ( )-cinnamyl alcohol (0.523 g, 4 mmol) in dry cumene (3mL) was added dropwise over a period of 0.5 h at — 10°C to a solution of n-BuLi/hexane (7.5 mL, 12 mmol) in the presence of (—)sparteine (0.92 mL, 4 mmol) in dry cumene (5mL). The red reaction mixture was stirred at 0 °C for 1 h. After cooling, the reaction mixture was poured into IMHCl. The aqueous layer was extracted with ether (2 X lOmL), and the combined organic phases were dried over MgS04. After evaporation of the solvent, the residue was chromatographed on silica gel (eluent 80 20 cyclohexane/ethyl acetate). Yield of (S)-93, 82% (0.632 g) 0 - = — 4.1° (c = 0.175, methylene chloride). 

Carbomers are synthetic, high-molecular-weight, crosslinked polymers of acrylic acid. These poly(acrylic acid) polymers are crosslinked with allyl sucrose or allyl pentaerythritol. The polymerization solvent used most commonly was benzene however, some of the newer commercially available grades of carbomer are manufactured using either ethyl acetate or a cyclohexane-ethyl acetate cosolvent mixture. The Carbopol ETD resins are produced in the cosolvent mixture with a proprietary polymerization aid, and these resins are crosslinked with a polyalkenyl polyether. 

A solution of 1.4 g (4.5 mmol) of ethyl-l-(4-methyl-3-pentenyl)-2-trimethylsilyloxy-cyclopent-2-enyl-l-carboxylate 4.15b and 103 mg (0.45 mmol) of 9,10-dicyanoanthracene (DCA) in 100 mL of dry acetonitrile was degassed by argon bubbling and distributed among 10 mL Duran glass tubes. After purging the tubes with argon for 1 min, they were sealed and irradiated for 100 h in a Rayonet reactor fitted with 450-nm lamps and a merry-go-round inset. The solvent was evaporated and purification by HPLC (20 x 250 mm LiChrosorb Si 60-5, cyclohexane/ethyl acetate 97 3) lead to 0.5 g (47%) of ethyl-... 

After cooling to room temperature, the nitromethane solvent was separated, evaporated and the remaining crude product purified by column chromatography (silica, cyclohexane/ethyl acetate), to obtain pure 1-biphenyl-4-yl-ethanone (yield 94%). 

Clean-up is the most important step for biological samples because they are rich in fat and lipids, etc. Liquid-solid chromatography and gel permeation chromatography (GPC) are widely used for the clean-up of extracts. GPC is very useful in removing fats from the extracts of biological samples. The most widely used gel column is SX-3 BioBeads (200-400 mesh) in a range of column sizes and solvents. The eluents used in GPC are mostly mixtures such as cyclohexane-ethyl acetate, cyclohexane-dichloromethane, toluene-ethyl acetate and... 

Figure 6.9. Separation of a mixture of estrogens by incremental multiple development with variable (A) and fixed (B) solvent entry position, and by multiple chromatography (C). A nine step sequence with the mobile phase cyclohexane-ethyl acetate (3 1, v/v) was used for (A) and (B) and seven 7 cm developments for (C), all on a silica gel HPTLC layer. The estrogens, in order of migration, are 17p-dihydroequilenin,...

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