Benzofenona y Fatlimida

Organic Syntheses, Vol. 8, p. 26 (1928); Coll. Vol. 1, p.95 (1941).
BENZOPHENONE
|
Submitted by C. S. Marvel and W. M. Sperry.
Checked by J. B. Conant and G. M. Bramann.
1. Procedure
In a 5-l. two-necked, round-bottomed flask fitted with a good mechanical stirrer (Note 1), a separatory funnel, a thermometer, and a reflux condenser connected with a trap (Note 2) for absorbing the hydrogenchloride evolved, are placed 455 g. (3.4 moles) of anhydrous aluminum chloride (Note 3) and 1 l. (10.2 moles) of dry carbon tetrachloride (Note 4). The flask is surrounded by an ice bath (Note 5). The stirrer is started and when the temperature of the carbon tetrachloride has dropped to 10–15°, 50 cc. of dry thiophene-free benzene (Note 6) is added all at once. The reaction begins immediately asis indicated by the evolution of hydrogen chloride and a rising temperature. As soon as the reaction has started, salt is added to the ice in the cooling bath in order to get more effective cooling. When the temperature begins to fall after the reaction has started, a mixture of 550 cc. (a total of 6.7 moles) of thiophene-free benzene and 550 cc. (a total of 14.5 moles) of carbon tetrachloride isrun in at such a rate that the temperature is kept between 5° and 10° (Note 5). If efficient cooling is maintained, this addition requires one to two hours. The stirring is continued for about three hours after the benzene-carbon tetrachloride solution has been added, while the temperature is held at about 10°. The stirring is then discontinued and the mixture is allowed to stand about twelvehours. During this time the mixture comes to room temperature.
The stirrer is then again started and about 500 cc. of water is slowly added. External cooling is used in order that the water may be added more rapidly. The excess carbon tetrachloride usually refluxes during this part of the procedure. The reaction mixture is then first heated on a steam bath to remove most of the excess of carbontetrachloride, then the mixture is distilled with steam to carry over the remaining carbon tetrachloride (Note 7), and to hydrolyze the benzophenone dichloride to benzophenone. The carbon tetrachloride comes over in about thirty minutes but the steam distillation is continued for about one hour to insure complete hydrolysis. The upper benzophenone layer is then separated from the aqueous layer and thelatter is extracted with about 200 cc. of benzene. The benzene solution and the benzophenone are transferred to a 1-l. modified Claisen flask (p. 130) for distillation. The benzene and any water that is present are removed under ordinary pressure and the benzophenone is distilled under reduced pressure (Note 8). The yield is 490–550 g. (80–89 per cent of the theoretical amount based on the benzene)of a product boiling at 187–190° /15 mm., and solidifying to a white solid melting at 47–48°. The material sometimes has a bluish tinge. This color may be removed and a colorless product obtained by moistening the material with benzene and centrifuging.
2. Notes
1. The stirrer should be very efficient, as otherwise the aluminum chloride tends to cake on the sides of the flask. This makescooling very difficult and thus increases the time necessary for the addition of the benzene-carbon tetrachloride mixture.
2. Gas Absorption Trap.—A convenient trap (Fig. 7) devised by John R. Johnson for the absorption of hydrogen chloride, or for the elimination of sulfur dioxide, hydrogen cyanide, etc., may be arranged as shown in the figure.
Fig. 7. |
|
The gases are led into a chamber inwhich a stream of water (from the reflux condenser in this case) flows downward into a large bottle. The bottle is provided with a bent tube which serves as a siphon drain. The gases are thus brought into contact with a flowing stream of water so that the heat of solution is dissipated, and the level of the water in the lower bottle serves as a seal to prevent escape of the gases into the...