Cold-finger condenser

Fig. XII, 2, 1). For very small volumes of liquid either of the apparatus depicted in Fig. XII, 2, 10, incorporating a cold finger condenser may be employed subsequent distillation (or steam distillation) is a facile...

Sublimation.—This is a valuable means for the purification of many organic substances and is admirably adapted for small scale work since losses are generally small. Sublimation may be carried out either at atmospheric pressure or under reduced pressure. The apparatus shown in Fig. XII, 2, 20 is simple and effective the sublimate is collected on the cold finger condenser. 

A cold finger condenser packeFriedrichs condenser in combination with a circulating low-temperature bath (— 70°) is more convenient. 

The checkers used a Dry Ice-acetone-cooled cold-finger condenser fitted with a partial take-off adapter. 

Another piece of glassware used in synthetic procedures is the cold finger condenser (Fig. A3.7). Used in the case where the reaction is carried out in a low-boiling solvent (for example, liquid ammonia), the condenser is filled with a suitable cooling mixture and fitted with a drying tube. 

A reaction vessel as shown in Fig. 1 is made from Pyrex tubing (Note 1). The vessel is evacuated and the stopcock closed. A 500-ml. round-bottomed two-necked flask equipped with a gas inlet and a cold finger condenser containing dry ice is charged with 1 g. of finely powdered 4,4 -bis(dimethylamino)benzophenone... 

Seventy grams (l mole) of freshly prepared potassium meth-oxide (Note 1) and 41 g. (1 mole) of freshly purified acetonitrile (Note 2) are placed in a 5 00-ml. distilling flask. A cold-finger condenser which extends into the bulb of the flask is inserted through a rubber stopper in the neck of the flask, and a short... 

A. (Tn fluoromethyl)trimethylsilane. A 2-L, three-necked flask is fitted with an efficient, over-head, sealed mechanical stirrer, a cold-finger condenser (30-cm in length and 8-cm in diameter) and a rubber septum (Note 1). The top outlet of the condenser is attached to an oil bubbler. The flask is flushed with dry nitrogen and charged with 118.8 g (1.09 mol) of chlorotrlmethylsilane (Note 2) in 100 mL of... 

The crude product is purified by decolorization with charcoal and recrystallization from 100-150 ml. of diisopropyl ether to give about 19-21 g. (27-30%) of colorless needles, m.p. 70-72°. This material is sufficiently pure for most purposes. Further purification may be achieved by further recrystaUization from diisopropyl ether and/or sublimation at 60° (0.1 mm.) onto a cold-finger condenser to give material melting at 73-74° (Note 9). 

Condenser - either silica cold finger condensers, effective length 140 mm, or soda glass air condensers, approximately 750 mm. 

Finally, the solution of 10,11-dibromohendecanoic acid in absolute ether is added slowly from a separatory funnel to the reaction flask. The reaction mixture is then stirred for 6 hours. After an additional 1 hour (Note 4) of stirring, during which time the cold-finger condenser is removed from the system, an excess of solid ammonium chloride (40 g., 0.74 mole) is introduced slowly into the reaction mixture to destroy excess sodam-ide. The ammonia is allowed to evaporate, 400-500 ml. of water is added, and the mixture is stirred until all the solid is broken up and dissolved (Note 5). 

The propyne is passed directly from the tank or lecture bottle to a cold-finger condenser filled with a slush of Isopropyl alcohol and dry ice. The condenser is attached to a 20n-mL, three-necked flask equipped with a gas-inlet adapter and a glass stopper. The flask has been previously calibrated to hold 85 mL of liquid. 

Cool the cold finger condenser of the simultaneous distillation extractor to 0°C, using a cooling bath. 

The temperature of the baths must be precisely adjusted. It is best if these baths are dedicated to these extractions. Likewise, the cold finger condenser must be maintained at 0°C, usually by the use of a cooling bath. The cooling temperature given by tap water (generally between 10° and 15°C) is not enough to... 

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