Vacuum aspirators

If the urethane is to be hydrolyzed immediately, there is no need to isolate it. Instead, after distillation of most of the ether and alcohol from the flask in which the urethane is formed, 700 ml. of concentrated hydrochloric acid is added, and the mixture is heated under reflux for 4 hours. The solution is then distilled from a steam bath under aspirator vacuum (Note 11), and the putrescine dihydrochloride is isolated as described above. The total yield is 55-57 g. (74-77%). 

A solution of 25.8 g. (0.20 mole) of 4-amino-2,2,4-trimethyl-pentane (ierf-octylamine) (Note 1) in 500 ml. of C.P. acetone is placed in a 1-1. three-necked flask equipped with a Tru-Bore stirrer and a thermometer and is diluted with a solution of 30 g. of magnesium sulfate (Note 2) in 125 ml. of water. Potassium permanganate (190 g., 1.20 moles) is added to the well-stirred reaction mixture in small portions over a period of about 30 minutes (Note 3). During the addition the temperature of the mixture is maintained at 25-30° (Note 4), and the mixture is stirred for an additional 48 hours at this same temperature (Note 5). The reaction mixture is stirred under water-aspirator vacuum at an internal temperature of about 30° until most of the acetone is removed (Note 6). The resulting viscous mixture is steam-distilled approximately 500 ml. of water and a pale-blue organic layer are collected. The distillate is extracted with pentane, the extract is dried over anhydrous sodium sulfate, and the pentane is removed by distillation at atmospheric pressure. The residue is distilled through a column (Note 7) at reduced pressure to give 22-26 g. (69-82%) of colorless 4-nitro-2,2,4-trimethylpentane, b.p. 53-5473 mm., < 1.4314, m.p. 23.5-23.7°. 

The solution is cooled to room temperature and is washed with a few milliliters of benzene into a single-necked flask. The solvent is removed with a rotary evaporator connected to a water aspirator vacuum gentle heat is supplied from a steam bath. The residue is cooled to room temperature before air is admitted. About 200 ml. of hexane is added and stirred with the residue to extract most of the carborane. The brownish tar which remains undissolved is allowed to settle and the solution is decanted. A second extraction of the tar with 40 ml. of hexane converts the residue to a solid which is removed by filtration. The solid is washed on the filter with an additional 40 ml. of hexane. The combined hexane extracts are filtered and then washed in a separatory funnel with four 100-ml. portions of a chilled aqueous 10% sodium hydroxide solution, followed by four 100-ml. portions of water. After the yellow hexane solution has been dried over anhydrous magnesium sulfate and filtered, the solvent is removed by use of a rotary evaporator connected to a water aspirator. The carborane is washed with a small amount of pentane into a 300-ml. single-necked flask which is attached to an alembic column as pictured in Fig. 13. 

The reaction flask is allowed to cool and the condenser, stirrer, and nitrogen inlet are removed. To the solution is added 100 ml. of absolute ethanol, and a brisk stream of carbon dioxide is passed through the solution to precipitate the excess potassium hydroxide as potassium carbonate. Sufficient carbon dioxide to precipitate the excess potassium hydroxide is conveniently obtained from about 150 g. of Dry Ice. The Dry Ice is powdered and placed in a stoppered 500-ml. filter flask with a line leading into the reaction solution. The insoluble potassium carbonate is filtered and washed with four 50-ml. portions of absolute ethanol. The combined filtrate and washings are evaporated to dryness on a rotary evaporator using a water aspirator vacuum and heat from a steam bath. This yields a solid or semisolid cake containing some residual potassium carbonate. 

Cycloheptanone was purchased from Aldrich Chemical Company, Inc. and distilled under aspirator vacuum through a 6-in. Vigreux column prior to use. 

The residue was distilled with a Kugelrohr apparatus under water aspirator vacuum (approximately 20mbar, 140 °C) to give (,SY)-methyl-(3)-hydroxy-butanoate (105 mg, 99%). 

B. 2,4-Dinitrobenzenesulfenyl chloride. Dry 2,4-dinitrophenyl benzyl sulfide (232 g., 0.80 mole) and 400 ml. of dry ethylene chloride are placed in a 2-1., one-necked, round-bottomed flask equipped with a stirrer (Note 3). Sulfuryl chloride (119 g., 0.88 mole) (Note 4) is added to the resulting suspension at room temperature. A mildly exothermic reaction causes the solid to dissolve quickly, usually within 1 to 2 minutes, with a temperature rise of 10-15° (Note 5). The resulting clear yellow solution is concentrated to an oil by heating under aspirator vacuum on a steam bath (Note 6). Caution Do not heat with gas or electricity because the product, like many nitro compounds, can explode if overheated.) The residual oil is cooled to 50-60°, and 3-4 volumes of dry petroleum ether (b.p. 30-60°) are added with vigorous handswirling. The oil quickly crystallizes. The mixture is cooled to room temperature and filtered to separate 2,4-dinitrobenzene-sulfenyl chloride as a yellow crystalline solid. The sulfenyl chloride is washed well with dry petroleum ether and dried at 60-80° (Note 7) weight 150-170 g. (80-90%) m.p. 95-96° (Notes 8, 9). 

The protein sample was then degassed under aspirator vacuum for a minimum of 20 min, with stirring, in order to remove excess dissolved gas forced into the solution during the diafiltration step. A sample of diafiltration buffer, to be used in filling the reference cell of the calorimeter, was given identical treatment. Buffers used were 50 mM acetate (pH 4.80), 43.4 mM 2-[N-morpholino]ethanesulfonic add (MES) (pH 6.32),... 

Tellurophene. A mixture of tellurium (4.0 g, 31 mmol), sodium formaldehyde sulphoxylate of 85% (28 g, 200 mmol), sodium hydroxide (17 g, 425 mmol) in 150 mL water is heated at reflux, under N2 atmosphere for 15 min, and then cooled at 20°C. A solution of 1,4-bis(trimethylsilyl)-l,3-butadiene (8.2 g, 42 mmol) in 100 mL of ethanol is slowly added to the stirred sodium telluride solution, the mixture is heated at reflux for 15 min, then stirred at 20°C for 3 h and extracted with ether. The extract is dried (Na2S04), filtered, and 10 mL (200 mmol) of bromine are added dropwise until the bromine colour persists. This solution is concentrated in a water bath under aspiration vacuum to a volume of 50 mL, and the red precipitate of tellurophene dibromide is collected 8.9 g (84%), m.p. 120°C dec. 

The crade product, suspended in 100 mL of diethyl ether is treated with a solution of sodium sulphite (21 g, 170 mmol) and potassium carbonate (16 g, 161 mmol) in 250 mL of water in a 500 mL separatory funnel. The mixture is shaken until aU the solid has disappeared, the ether layer is separated, the aqueous layer is extracted with ether and the combined organic phase is washed with water, dried (Na2S04) and evaporated (aspiration vacuum) giving the yellowish oil of pure tellurophene 3.3 g (59%), b.p. 102°C/350 torr (partial dec.). 

Telluraxanthene Bis(2-bromophenyl)methane (3.33 g, 1.02 mmol) is dissolved in 300 tuL of absolute diethyl ether and, under dry nitrogen, 22 mL (36.1 mmol) of a 15% solution of n-butyllithium in hexane are added dropwise. The mixture is heated under reflux for 0.5 h, cooled to 20°C and 1.8 g (14.1 mmol) of finely powdered tellurium are added. The resultant mixture is heated under reflux for 2 h and then poured into ice/water. The mixture is extracted with chloroform, the extract is filtered and the solvent is evaporated in a rotatory evaporator at 20°C under aspirator vacuum. The residue is recrystallized from diethyl ether/petroleum ether after addition of activated charcoal. Yield 1.42 g (47%) m.p. 151°C. 

Bis(dimethyl hydrogen phosphite-/ )bis(dimethyl phosphito-P)platinum(lI) (0.420 g, 0.66 mmole) and c/s-[dichlorobis(triphenylphosphine)platinum(ll)] (0.524 g, 0.66 mmole) are refluxed in toluene (25 mL) for 30 hours. The colorless reaction mixture is filtered while hot using vacuum to remove any unreacted c/s-[dichlorobis(triphenylphosphine)platinum(Il)]. The filtrate is transferred to a 100-mL, round-bottomed flask and evaporated to dryness on a rotary evaporator, using gentle heating if necessary. The cream-colored residue is dissolved in a mixture of dichloromethane (15 mL) and methanol (15 mL) and the solution is allowed to concentrate slowly under water aspirator vacuum on a rotary... 

The checkers found it more convenient to remove the volatile material at this stage by warming the stirred mixture at 40° using a water aspirator vacuum (10 mm.). About 3 hours were required. 

The pentane and other volatiles are removed by fractional distillation using a 5-cm. steel-wool-packed column and heating the pot in a 70° oil bath (Note 4). A water aspirator vacuum is applied, and 18.2-22.9 g. (36-45%) of the diene 1 is distilled as a colorless oil, b.p. 50-55° (50 mm.) (Note 5). On a smaller scale, yields of up to 50% have been obtained. 

The reaction mixture is quenched by the addition of 25 mL of ice water, and slowly acidified to pH 2 with 75 ml of 3 N hydrochloric acid. The organic layer is separated and the aqueous layer is extracted with three 75-mL portions of ether. The extracts are combined with the original ether layer, washed successively with 50 mL of water, two 50-mL portions of aqueous 10% sodium bicarbonate, and 50 mL of saturated sodium chloride solution, and dried over anhydrous magnesium sulfate. After the magnesium sulfate is removed by filtration, the solvent is removed at aspirator vacuum on a rotary evaporator and the residue 1s distilled through a short column to give 8.8-10.2 g (66-76%) of 3-phenylpropionaldehyde, bp 87°C (1.0 mm) (Notes 5, 6, and 7). 

The submitter reports that the commercial 95% Sodium Methylate from Mathieson Chemical Corp. is satisfactory, provided that either fresh material or material which has been opened previously only under dry nitrogen is used. The checkers experienced such erratic results with commercial sodium meth-oxide (even previously unopened bottles) that freshly prepared material was used. For this purpose, 37 g. of clean sodium, cut in 1- to 3-g. pieces, was added portionwise to 800 ml. of stirred anhydrous methanol contained in a 2-1. three-necked flask equipped with a condenser. After the sodium had dissolved, the methanol was removed by distillation at reduced pressure, and the residual white sodium methoxide was dried by heating at 150° under aspirator vacuum. 

Filter the homogenous sample through a Whatman no. 2 filter paper into a chilled 500-ml filter flask by water-aspirated vacuum suction using a chilled Buchner funnel. Pour the homogenate slowly into the center of the filter paper and allow to advance to the edges before applying the vacuum. 

A. Trimethyl 2-chloro-2-cyclopropylidenorthoacetate. A 1-L, two-necked, round-bottomed flask equipped with a mechanical stirrer and a reflux condenser is charged with 40.0 g (0.19 mol) of 1-chloro-1-(trichloroethenyl)cyclopropane (Note 1), 120 g of potassium hydroxide, and 300 mLof methanol (Note 2). The mixture is stirred for 16-18 hr in an oil bath at 85°C. After the solution is cooled to room temperature, it is diluted with 1 L of ice water. The mixture is then transferred to a 3-L separatory funnel and extracted with three 200-mL portions of ether. The combined ether phases are washed with three 150-mL portions of saturated brine, dried over anhydrous magnesium sulfate, and filtered. The solvent is removed from the filtrate by distillation at atmospheric pressure, and the residue is distilled through a short-path column under water-aspirator vacuum to give 14.5-15.4 g (39-41%) of trimethyl 2-chloro-2-cyclopropylidenorthoacetate, bp lOS-IOS C (20 mm) (Notes 3 and 4). 

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