Water aspirators

Procedure for filtering through a filtering crucible. The trap is used to prevent water from a water aspirator from backwashing into the suction flask. 

The function of the trap is to condense the hexane from the n-butyl-lithium solution. The checkers used a 1-L three-necked flask fitted with a short delivery tube (a quick fit air bleed tube was used), stopper, and rubber tubing connection. The submitters used a water aspirator and a 1-L filter flask with a drying tower between. 

In a 2-1. three-necked round-bottomed flask, fitted with an efficient sealed stirrer and a reflux condenser capped by a drying tube, are placed the dried anisyl chloride (Notes 2 and 3), 73.6 g. (1.5 moles) of finely powdered sodium cyanide, 10 g. of sodium iodide, and 500 ml. of dry acetone (Note 4). The heterogeneous reaction mixture is heated under reflux with -sngorous stirring for 16-20 hours, then cooled and filtered with suction. The solid on the filter is washed with 200 ml. of acetone and discarded (Note 5). The combined filtrates are distilled to remove the acetone. The residual oil is taken up in 300 ml. of benzene and washed with three 100-ml. portions of hot water. The benzene solution is dried over anhydrous sodium sulfate for about 15 minutes, and the solvent is removed by distillation at the reduced pressure of the water aspirator (Note 6). The residual -methoxyphenyl-acetonitrile is purified by distillation under reduced pressure through an 8-in. Vigreux column b.p. 94—97°/0.3 mm. 1.5285-1.5291. The yield is 109-119 g., or 74-81% based on anisyl alcohol (Notes 7 and 8). 

The checkers removed the ammonia by distillation (water aspirator). 

A solution of 30 g (0.1 mole) of 17j5-hydroxy-5a-androstan-3-one (androstano-lone), 20 ml of pyrrolidine and 200 ml of benzene is heated at reflux temperature for 2.5 hr under a Bidwell-Sterling water trap. The benzene solution is evaporated to dryness in a rotating evaporator connected to a water aspirator. The white cake which remains is broken up and dried further by immersing the flask in a water bath at 60-75° and evacuating the flask with a mechanical vacuum pump. After 0.5 hr the solid cake is broken up again and dried for another 0.5 hr at 60-75°. The enamine (9) obtained should smell only faintly of pyrrolidine. 

After chilling to -t-12°C, additional methanol (35 ml) and a concentrated aqueous ammoniurt hydroxide solution (1.4M) (100 ml) are added and stirring is continued for 2 hours at a temperature maintained at from -t-5° to -H5°C. The organic layer is separated and solvent is stripped from the aqueous layer at water aspirator pressure at a temperature below 40°C. The residue is extracted several times with chloroform and the chloroform extracts are combined with the separated oil. Chloroform is removed at water aspirator pressure at a temperature below 35°C to leave crude q-amino- -methylmercaptobutyronitrile (methionine nitrile) in 88% yield (68 g) as a clear, somewhat viscous oil. 

Trimethylamine oxide is normally available as a hydrate, and for the present preparation it is necessary to convert it to its anhydrous form. A convenient way of doing this is as follows. A solution of 45.0 g. of trimethylamine oxide dihydrate (supplied by Beacon Chemicals) is dissolved in 300 ml. of warm dimethyl-formamide and placed in a three-necked flask set up for distillation. At atmospheric pressure the flask is heated and solvent distilled off until the boiling point reaches 152-153°. Then the pressure is reduced using a water aspirator, and the remainder of the solvent is distilled. At the end of the distillation the temperature of the bath is slowly raised to 120°. The residual anhydrous trimethylamine oxide (30 g.) can be dissolved in 100 ml. of chloroform and may remain in the same flask for use in the present preparation. 

To a freshly prepared solution of 11.3 g. (0.10 mole) of hydrox-ylamine-O-sulfonic acid (Note 1) in 64 ml. of cold water there is added 24 ml. (24 g., 0.30 mole) of pyridine (Note 2). The mixture is heated at about 90° on a steam bath for 20 minutes. It is then cooled to room temperature with stirring, and 13.8 g. (0.10 mole) of potassium carbonate is added. The water and excess pyridine are removed from the mixture by heating it at 30-40° in a rotatory evaporator in conjunction with a water aspirator. The residue is treated with 120 ml. of ethanol, and the insoluble precipitate of potassium sulfate is removed by filtration. 

The checkers used a sintered glass pressure filter (Coming Glass Works, Cat. No. 34020) rather than a suction filter in order -to minimize evaporation losses. An ordinary water aspirator can cause the mixture to boil at room temperature. The flask and filter can be cleaned readily with a little acetone, which dissolves mercuric bromide rapidly. 

The mixture is extracted with four 100-ml. portions of methylene chloride. The extracts are combined, washed successively with 100 ml. of water and four 100-ml. portions of 5% sodium carbonate solution (Note 4), and dried over anhydrous magnesium sulfate. The methylene chloride is removed by evaporation at 30-40° under the pressure of a water aspirator, and the residue is distilled through a 30-cm. Vigreux column to yield 85-90 g. (65-69%) (Note 5) of acetone cyanohydrin nitrate (Note 6) b.p. 62-65°/10 mm. 1.4170-1.4175 (Note 7). 

B. N-Nitromorpholine. Morpholine (34.8 g., 0.40 mole) and 26 g. (0.20 mole) of acetone cyanohydrin nitrate are mixed in a 50-ml. round-bottomed flask equipped with a thermometer well. A condenser is attached, and the mixture is heated slowly. At about 60° an exotherm ensues that raises the temperature of the mixture to 110°. The mixture is allowed to cool to 80° and maintained there for 1 hour. It is poured into 200 ml. of 10% hydrochloric acid (Caution Do in a hood Note 8) and extracted with three 100-ml. portions of methylene chloride (Note 9). The extracts are combined, washed successively with two 100-ml. portions of water, 100 ml. of 10% hydrochloric acid, and 100 ml. of water, and dried over anhydrous magnesium sulfate. The solvent is removed by evaporation on a water aspirator at room temperature to yield a pale-yellow oil (Note 10). 

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 checkers recommend that excessive heating and evacuation be avoided dming rotary evaporation to minimize the loss of product during this operation. They kept the heating bath temperature below 80° and used a water aspirator. 

Pyridinecarboxaldehyde (nicotinaldehyde) was supplied by Aldrich-Europe, Beerse, Belgium. The checkers purified this reagent by fractional distillation, b.p. 95-97° (15 mm.). The submitters stress that 3-pyridinecarboxaldehyde should be completely free from contamination by the acid. They stirred 150 g. of the aldehyde with 100 g. of potassium carbonate and 300 ml. of ethanol for 12 hours, filtered the suspended solid, and fractionally distilled the filtrate through a 30-cm. Vigreux column using a water aspirator. However, the checkers found that the recovery of aldehyde from this procedure was very low, and recommend vacuum distillation instead. 3-Pyridinecarboxaldehyde is a powerful skin irritant and should be handled with protective gloves. 

The dimensions of the column used by the checkers were the same as those specified in Note 12, and the product was obtained from fractions 10-20. The submitters evaporated the rmclions with a rotary evaporator operated at water aspirator... 

Beakers 10 to 1000-ml. volumetric flasks 1-ml. volumetric pipet, serological pipet steam bath vacuum desiccator vacuum pump and water aspirator are also required. 

The hexane is evaporated completely at room temperature by placing the cells in a vacuum desiccator attached to a water aspirator. The evaporation requires 10 to 20 minutes. A drop of oily residue remains. This evaporation is handled conveniently by placing the cells in a beaker containing a 2.5-cm. level of mineral oil at room temperature and transferring the whole to the desiccator. The oil bath prevents excessive cooling of the hexane solution during the evaporation. 

Considerable dissolved hydrogen chloride is liberated at this point and passes into the water aspirator. A mechanical vacuum pump should not be used at this stage because it would be damaged by corrosion. 

B. Pyridine-N-oxide. The acetic acid solution is evaporated on the steam bath under the pressure of a water aspirator, and the residue (180-190 g.) is distilled at a pressure of 1 mm. or less in an apparatus suitable for collecting a solid distillate (Note 5). The vacuum pump must be protected with a Dry Ice trap capable of holding about 60 ml. of acetic acid, which distils as the pyridine-N-oxide acetate dissociates at low pressure. Heat is provided by an oil bath, the temperature of which is not allowed to rise above 130° (Note 6). The product is collected at 100-105°/1 mm. (95-98°/0.5 mm.). The yield is 103-110 g. (78-83%) of colorless solid, m.p. 65-66° (sealed capillary). The base is deliquescent and must be stoppered immediately. 

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