Ethyl acetate/water medium

Medium polar (Polyphenols, Terpenoids) Chloroform/Methanol/Water Methy-t-butyl ether/Acetonitrile/Water Heptane/Ethyl acetate/Water... 

With the powerful formylation reagent IV -diformylacetamide imides are obtained from amides or lactams in good yield (equation 56). Oxidation reactions also have found some application in the synthesis of imides. For example, catalytic amounts of ruthenium tetroxide and 10% aqueous NaI04 as cooxidant in an optimized reaction medium (ethyl acetate-water) oxidize acyclic amides to imides. The reaction rate is inversely related to the electron-withdrawing power of the acyl group, i.e. the electron density at the nitrogen atom (equation 57). 

Esters of medium volatility are capable of removing the water formed by distillation. Examples are propyl, butyl, and amyl formates, ethyl, propyl, butyl, and amyl acetates, and the methyl and ethyl esters of propionic, butyric, and valeric acids. In some cases, ternary azeotropic mixtures of alcohol, ester, and water are formed. This group is capable of further subdivision with ethyl acetate, all of the ester is removed as a vapor mixture with alcohol and part of the water, while the balance of the water accumulates in the system. With butyl acetate, on the other hand, all of the water formed is removed overhead with part of the ester and alcohol, and the balance of the ester accumulates as a high boiler in the system. 

By using a mixture of ethyl acetate and D2O as solvent for hydrogenation, up to 75% deuterium is incorporated in the reduced product.13 This result indicates that the role of water here is not only as a solvent. Research on asymmetric hydrogenation in an aqueous medium is still actively being pursued. The method has been applied extensively in the synthesis of various amino acid derivatives.14... 

Water also causes a change in the reaction medium, which may be advantageous. A drawback of the reducing medium in the Eastman process is that in addition to acetic anhydride, the by-product ethylidene diacetate is formed, CH3CH(AcO)2. This can be thermally decomposed to vinyl acetate and acetic acid, or it can be reduced to ethyl acetate, which in the recycle would lead eventually to propionic acid. 

Colloidal Dispersions or Solutions (Sols) and Colloids. Colloidal solutions (or rather "pseudo solutions ), also called sols (or in case of liquids hydrosols) are heterogeneous systems consisting of a "dispersion medium (mostly a liquid) and a "dispersed or "suspended medium known as a "colloid . Colloidal particles are invisible under ordinary microscope but detectable by the ultramicroscope. Their size ranges from ca 1 x 10 7 to 1 x 5 smm. If the dispersion is a viscous, sticky, transparent liquid, it is what is generally known as a "colloidal solution . As examples of this may be cited a soln of gum-arabic in water and sol ns of NC in acetone, ethyl acetate or ether alcohol. When "solns are dialized, most of the colloidal particles do not pass thru the membrane. This is their principal distinction from "crystalloids , which are substances like Na chloride, etc. If part of the volatile liquid (dispersing medium), is evaporated the resulting tacky, jellylike substance is known as a gel. 

Photolyses of the solid cyclodextrin complexes 1 were carried out with a Hano-via 450-W medium-pressure Hg lamp for 3 h at room temperature in a quartz vessel under vacuum. The photolysis vessel was tumbled continuously during the irradiation to ensure homogeneous photolysis of the sample. Conversions were limited to less than 20%. After photolysis, the solid complexes were dissolved in excess water and extracted with diethyl ether and chromatographed with hexane-ethyl acetate (5 1) to isolate the products in pure form. Irradiation of solid / -cy-clodextrin complexes of benzaldehyde resulted in an intramolecular reaction to give benzoin (/ )-(-)-2 and 4-benzoylbenzaldehyde 3 (7 3, 80%). 

An emulsion of 1 (1 g, 2.77 mmol) in distilled water (150 mL) was irradiated using a 450-W medium-pressure Hanovia lamp and a Pyrex filter for 36 h with stirring. The photolyzed mixture was extracted with dichloromethane. Removal of tlie solvent in vacuo gave a thick residue. It was then stirred with methanol for about 6 h. Solvent was removed in vacuo to give a residue that was chromatographed over a silica gel column. Elution with a mixture of 15% ethyl acetate in PE gave 3 as a white solid, mp 41 °C (230 mg, 21%), which was crystallized with difficulty from a mixture of n-pentane and dichloromethane (4 1). 

A suspension of the compound (0.5-1 g) in distilled water (150 mL) was irradiated with stilling using a Hanovia medium-pressure 450-W lamp and a Pyrex filter for ca. 35 h. The suspension was then extracted with CH2CI2 and the residue obtained after removal of solvent was chromatographed on a silica gel column (60-120 mesh). The ketene was eluted with a mixture of ethyl acetate (5-10%) in petroleum ether (bp 60-80 °C). 

The kinetics of the reaction between bromopropionate and thiosulfate ions have been studied at 10-40 °C in various ethanol-water mixtures.107 Activation parameters were evaluated as a function of ionic strength and dielectric constant of the medium. The medium effect of mixed solvents on the rate constants of the Menshutkin reaction of triethylamine with ethyl iodide has been studied for binary mixtures of cyclohexane with benzene or ethyl acetate,108 and with chlorobenzene or dimethoxyethane.109 Rates were measured over the temperature range 293.1-353.1 K, and activation parameters were determined. 

After cooling of the medium, 120 ml of water containing 11.6 g of sodium carbonate and ether are introduced, the aqueous phase is decanted and washed with ether, whereupon the aqueous phase is acidified to a pH of 1 with 50% hydrochloric acid. The desired product is extracted with ethyl acetate. After elimination of the extraction solvent 31.5 g of the 4-(3,4,5-trimethoxyphenyl)-4-oxo-2-hydroxy butanoic acid, melting point 119°-120°... 

The above chloro intermediate product, 3 g and 3.5 g of tropine with 25 ml of toluene as reaction medium are refluxed for 3 hrs. The reaction mixture is then concentrated in a vacuum until the solvent and other volatile materials are removed. The residue is treated with dilute aqueous hydrochloric acid, and ether. The aqueous layer is separated and neutralized with aqueous sodium hydroxide. Insoluble material, which thereupon separates is dissolved in ether, and the ether solution separated. It is washed several times with water, dried and evaporated, leaving the free base form of the desired product (zepastine) which crystallizes on standing, MP 157°C. It is recrystallized from ethyl acetate, MP 162°C. 

Esters, tertiary amides, and nitriles are frequently used as solvents for organic reactions because they provide a polar reaction medium without O—H or N—H groups that can donate protons or act as nucleophiles. Ethyl acetate is a moderately polar solvent with a boiling point of 77 °C, convenient for easy evaporation from a reaction mixture. Acetonitrile, dimethylformamide (DMF), and dimethylacetamide (DMA) are highly polar solvents that solvate ions almost as well as water, but without the reactivity of O—H or N—H groups. These three solvents are miscible with water and are often used in solvent mixtures with water. 

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