Production precipitation

Aluminum acetylsaHcylate is a tasteless, nonbasic, stable, alternative therapeutic salt to aspirin (83). Also called aluminum aspirin, it is an insoluble white to off-white powder prepared by reaction of aluminum isopropoxide with sodium acetylsaHcylate in an organic solvent. The product precipitates from the reaction mixture (83). Standards requke that aluminum aspirin contain not less than the equivalent of 80% aspirin, corresponding to 90% purity on an anhydrous basis. The aluminum oxide assay must be 12—17% (81). 

Gibbsite usually contains several tenths of a percent of alkaU metal ions the technical product, precipitated from a sodium aluminate solution, contains up to 0.3% Na20 wliich carmot be washed out even using dilute HQ. Several authors (1,2) suggest that these alkaU ions are an essential component of gibbsite structure. 

TYZOR ET is reduced by sodium and ethanol to a dark-blue compound (182). Use of potassium as the reducing agent in the alcohol permits the isolation and identification of Ti(OC2H2)3 [22922-82-3] and Ti(OC4Hg)3 [5058-41-3] (183,184). The products precipitate as soUd alcoholates,... 

Recovery of Uranium from Leach Solutions. The uranium can be recovered from leach solutions using a variety of approaches including ion exchange (qv), solvent extraction, and chemical precipitation. The most common methods in practice are ion exchange and solvent extraction to purify and concentrate the uranium prior to final product precipitation. 

Natural ground calcium carbonate has been used for years as the primary constituent of putty. Since 1945, the processing of natural calcium carbonate has seen the introduction of beneficiation by flotation (qv) to remove impurities and the development of grinding processes to manufacture finer products. Precipitated calcium carbonate was first introduced in England in 1850 commercial production started in the United States in about 1913. 

During one run, 48 g. of product precipitated from the tetrahydrofuran reaction mixture. This precipitate was filtered, washed with saturated, aqueous sodium chloride, water, and petroleum ether (b.p. 35-60°) to yield a crystalline product, m.p. 99-106°. For recovery of the remaining product, the tetrahydrofuran filtrate was worked up in accordance with the described procedure. 

Preparation of 3a-Hydroxy-5) -pregn-17(20)-en-21-oic Acid . A solution of 15 g of 3a-acetoxy-5jS-pregnan-20-one in 290 ml of glacial acetic acid is treated with 13 g of bromine at room temperature. After complete addition of bromine the reaction mixture is heated at 40-50° for 30 min, and the product precipitated with water and filtered. The product is taken up in ethyl acetate (500-600 ml) and the resulting solution washed with dilute aqueous potassium bicarbonate. The solvent is concentrated in vacuo and the product crystallized from acetone to give 16g of dibromide mp, 173-175°. 

The chloroform layer is washed with a dilute aqueous sodium hydroxide solution, thereafter with water, and is finally dried over potassium carbonate. The residue, which is obtained after evaporation of the chloroform, is dissolved by heating in a mixture of 25% of toluene and 75% of heptane. On cooling this solution to about 20°C the product precipitates. That compound is reduced with LiAIH4 to give cinnarizine. 

The ether is left to stand at a low temperature below 10°C when the remaining portion of the product precipitates and is filtered off and added to the first precipitate. The product thus obtained is thoroughly washed, first in water and then in a solution of sodium bicarbonate, and then agein in water. After drying in air, the product is crystallized from anhydrous ethanol or from acetone and water. The analytical data correspond to calculated values. Yield is 18 g MP 122°Cto 124°C. 

Isopropyl-4(or 5-nitroimidazole) (31 g = 0.2 mol), dioxane (70 g) and dimethylsulfate (28 g = 0.22 mol) were heated on a steam bath under reflux for 45 minutes. The solvent was removed in vacuo on a steam bath, the residue dissolved in 20 ml of water and the product precipitated by the gradual addition of 80 g of 25% sodium hydroxide solution at 0°C. A small additional amount was obtained by extraction of the mother liquor with methylene chloride. The product melted at 60°C. 

The product was purified as follows. 60 g of product was dissolved in 3N aqueous hydrochloric acid, the solution was treated with charcoal and filtered. The filtrate was neutralized by the gradual addition of aqueous concentrated ammonia at 0°C to 5°C under stirring whereupon the product precipitated in white plates as the neutralization proceeded. The precipitate was filtered by suction, washed on the filter with 50 ml of ice cold water and dried at room temperature, MP 60°C. 

A solution of 2o, 3o, 16o, 17o -diepoxy-17/3-acetoxy-5o -androstane (25 grams), prepared from 3,17-diacetoxy-5o -androstane-2,16-diene Chem. Abs. 1960, 54, 8908) by treatment with m-chlor-per-benzoic acid, in piperidine (120 ml) and water (40 ml) was boiled under reflux for 5 days, the solution was concentrated and the product precipitated by the addition of water. The solid was collected, dissolved in dilute hydrochloric acid, filtered to give a clear solution and precipitated by the addition of sodium hydroxide soiution. Crystalliza-... 

The mixture was twice extracted with 75 ml of chloroform and the aqueous phase was evaporated in vacuo. The sodium salt was then dissolved in 150 ml of chloroform, the solution was dried over sodium sulfate and the product precipitated with anhydrous ether. 

The sulfate on the filter was dissolved in 200 ml of hot water, the solution charcoaled hot, and the product precipitated from the clear colorless filtrate by the gradual addition of a... 

In the first publication describing the preparative use of an enzymatic reaction in ionic liquids, Erbeldinger et al. reported the use of the protease thermolysin for the synthesis of the dipeptide Z-aspartame (Entry 6) [34]. The reaction rates were comparable to those found in conventional organic solvents such as ethyl acetate. Additionally, the enzyme stability was increased in the ionic liquid. The ionic liquid was recycled several times after the removal of non-converted substrates by extraction with water and product precipitation. Recycling of the enzyme has not been reported. It should be noted, however, that according to the log P concept described in the previous section, ethyl acetate - with a value of 0.68 - may interfere with the pro-... 

As the film dissolves more oxide film is formed, i.e. the metal/oxide interface progresses into the metal, and the overall rate may be low enough to be acceptable for a particular process. In other cases, the corrosion products precipitate on the surface of the oxide and either accelerate the overall rate by enhancing diffusion of ions through the porous outer layers or, when less porous layers are formed, access of hydrogen ions to the inner oxide surface is reduced thus decreasing the rate. 

Under N2, clean Li metal (0.17 g, 25 mmol) was placed in a round-bottom flask with a solvent mixture of MeOH (3 mL) and pcntan-t-ol (17 mL). The mixture was heated under N, until the reaction with Li was complete. Then, naphthalene-2,3-dicarbonitrilc (2 g, 11 mmol) was added to the mixture which turned green-brown the mixture was refluxed for 3h. The brown powder, obtained after cooling and removal of the solvent under reduced pressure, was dissolved in anhyd acetone (20 mL) and then hexane (70 mL) was added. The green precipitate was separated from the brown solution by filtration. This purification by precipitation was repeated twice. The green precipitate was placed in a Soxhlet extractor and extracted for 3 h with acetone (200 mL) in order to separate the product from the insoluble metal-free species and LiOH. The acetone solution was evaporated down to a volume of 20 mL. The product precipitated after the addition of hexane (70 mL). This latter purification step was performed several times yield 1.29 g (64%). 

The reaction is a free-radical alkylation in which radicals are derived from a carboxylic acid by decarboxylation with Ag+/S20a-. If has the advantage that the reaction medium can be adjusted so that the monoalkylatcd product precipitates as it is formed, whereby di- or polyalkylation5 is suppressed. 

In the case of products prepared from hydrolysis/condensation reactions, the time of reaction varies from a few hours to more than 3 months. Generally, the crude products precipitate from the reaction mixture and pure compound can be obtained by simple filtration followed by washing or recrystallization. However, the yields are often low and rarely exceed 50%. 

KR was an alcalase subtilisin Carlsberg as the major enzyme component). To avoid racemization of the final product, they employed a mixture of 2-methyl-2-propanol/ H2O (19 1). Under these conditions, the product precipitated during the course of hydrolysis (Figure 4.26). A very similar DKR process was reported two years later by Parmar [52]. 

The reaction at Eq. (12) allows the preparation of Na2S4 and K2S5 from the alkali metals, hydrogen sulfide and sulfur in anhydrous ethanol (ROH). First the metal is dissolved in the alcohol with formation of ethanolate (MOR) and hydrogen. Bubbling of H2S into this solution produces the hydrogen sulfide (MHS). To obtain the polysulfide the solution is refluxed with the calculated amount of elemental sulfur. After partial evaporation of the solvent and subsequent cooling the product precipitates. 

A condensation reaction where a product precipitates as a solid A batch alkylation where a gaseous alkene is continuously charged... 

In a solution, when the ionic product becomes equal to the solubility product, the solution is said to be saturated. If the ionic product is less than the solubility product, the solution is said to be unsaturated. When the ionic product is greater than the solubility product, precipitation of the electrolyte occurs. 

Synthesis of 3-Phenyltetrazolopyridinium bromide (119). 660 To a solution of 2.88 g of l-(2-pyridyl)-3-phenyltriazine was added 4.92 g of 2,4,4,6-tetrabromocyclohexa-diene-l-one. The product precipitated within minutes and was isolated by filtration in 87% yield mp 278—280 °C. 

The first step involved the reaction of PPO with chlorosulfonic acid according to a literature method (H). The sulfonated PPO was hygroscopic and unstable. We succeeded (12) in converting the sulfonate groups into stable sulfone groups by reacting them with aromatic compounds at elevated temperatures (120 0. The final dark solution was washed with dilute sodium bicarbonate, and the product precipitated in methanol, filtered and dried. 

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