Vacuum distillation under diminished pressure

DISTILLATION UNDER DIMINISHED PRESSURE ( VACUUM DISTILLATION)... 

Distillation under diminished pressure ( vacuum " distillation)... 

The nitrobenzene is then removed by vacuum distillation using a 2-1. Claisen flask, and the residue in the flask is distilled under diminished pressure the fraction boiling at 180-195°/ 15 mm. is collected (Notes 8 and 9). The red-yellow oil, which solidifies on cooling, amounts to 128-176 g. (40-55%) and is sufficiently pure for some purposes (Note 10). A nearly white product can be obtained by dissolving the crude product in ether, shaking the ether solution with portions of 5% sodium hydroxide solution until no color appears in the aqueous layer, evaporating the ether, and recrystallizing the residue from a mixture of petroleum ether (b.p. 60-90°, Skellysolve B) and benzene (Note 11). The recrystallized product melts at 83-84° the recovery is 80-85%. 

Vacuum distillation, see Distillation under diminished pressure Vacuum receivers, 103, 108, 109, 118, 218f... 

Vacuum distillation of the product is essential. Moreover in this final distillation the precautions mentioned (the use of an oil-bath and an outside temperature of less than 130°) must be carefully observed. When the furfural is distilled under ordinary pressure or when it is distilled under diminished pressure with a free flame, a practically colorless product is at first obtained. After a few days and sometimes after a few hours this product will gradually darken until finally a black liquid results. This change, although most marked in the presence of light, takes... 

The flask is cooled, 1-2 g. of Norite added with stirring, and the solution filtered with suction through a hardened filter paper (Note 6). The xylene is removed from the nearly colorless filtrate by flash distillation under diminished pressure. For this purpose, a 125-cc. modified Claisen flask is arranged for vacuum distillation, the usual capillary being replaced by a separatory funnel whose stem extends to the bottom of the flask. The... 

Naphthylacetonitrile. Place a mixture of 56g (0.32mol) of l-(chloro-methyl)naphthalene, 29 g (0.45 mol) of potassium cyanide, 125 ml of ethanol and 50 ml of water in a 500-ml round-bottomed flask fitted with a double surface reflux condenser, and reflux for 1 hour. Distil off the alcohol, transfer the residue to a separatory funnel, wash it with water, filter from a small amount of solid, transfer to a dish and dry under reduced pressure (vacuum desiccator charged with anhydrous calcium chloride). Distil under diminished pressure and collect the 1-naphthylacetonitrile at 155-160°C/9 mmHg (1) the yield is 38 g (72%). 

B) Preparation of Quinoline (M.). The results are generally better by the macro method. Use five times the amount of reagents, and a 500-ml reaction flask. The condenser should be very efficient. Use same precautions given for the micro method in starting the reaction, and allow it to proceed without external application of heat for 15-20 minutes. Boil for four hours. Transfer the mixture to a two-liter Florence flask for steam distillation. Steam-distill until about 1500-1700 ml of distillate has been collected. Use three 60-ml portions of ether with a separatory funnel to extract the distillate, and for the remainder of the experiment proportionate amounts of reagents. After the final extraction and recovery of ether use a small flask for the final distillation. If a vacuum pump is available, use a small Claisen flask and distill under diminished pressure. Collect the fraction which boils at 116-122 at 20 mm pressure. 

Pyridine 1-oxide A solution of pyridine in glacial acetic acid is warmed with an excess of 30% hydrogen peroxide at 70-80° for several hours and then concentrated in a vacuum, basified, and extracted with chloroform. The product is purified by distillation under diminished pressure. 

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