JOURNAL O F CHEMICAL EDUCATION
ORGANIC SYNTHESES ILLUSTRATING SEALED TUBE TECHNIQUES OLIVER GRUMMITT and JEANFICK Western Reserve University, Cleveland, Ohio
RECENTLY
our graduate course in Organic Syntheses mas converted to a new course, Laboratory Techniques in Organic Chemistry. The objective is to teach the theory and practice of the important laboratory operations, such as fractional distillation, fractional crystallization, adsorption, etc., in order to prepare the new graduate student for research work either on a doctoral thesis or in a commercial laboratory, if his training ends with the master's degree. This has required the selection and preparation of a whole group of new experiments, since conventional laboratory manuals emphasize organic preparations rather than technique. Among the experiments that were somewhat difficult to devise were those illustrating various types of pressure reaction vessels such as sealed glass tubes, pressure bottles, and high-pressure bombs. To provide practice in the use of sealed tubes of the Carius type, two smallscale organic syntheses were adapted from research work done in this laboratory and from the literature. In the belief that these directions would be of value to other instructors who are organizing similar courses, we are reporting these preparations here. In the first experiment p,pf-dichlorobenzil is made from 1,l-di - (p - chlorophenyl) - 2,2,2 - trichloroethane (DDT) in three steps. In the last step a hydrolysis run a t 19&200° is carried out in a sealed tube. The second synthesis yields hexaphenylbenzene via the condensation of tetraphenylcyclopentadienone (tetr* cyclone) and stilbene a t 250' in a sealed tube. Only
moderate pressures are developed in these experiments, and no tube has exploded in the course of about twenty runs. F i s t , the laboratory instructor demonstrates the cleaning, loading, sealing, and opening of a Pyrex Carius tube, 18 by 25 by 600 mm. (Corning 8620, FOQOE).' Each student practices sealing and opening until the instructor is satisfied that he is ready to go on. In the k s t preparation detailed directions for this operation are given, but these are not repeated in the second. In the first of three steps 1,l-di-(p-ch1orophenyl)-2,2,2-tricbloroethane is photochemically chlorinated t o give 1,1-di(p-chloropheny1)-1,2,2,2tetrachloroethane (1);this is isomerized to 1,kIi-(pchloropheny1)-1,1,2,2tetrachloroethane (2),which is then hydrolyzed to p,pfdichlorobenzil (2): (pCICeH4),CH-CCla (pClC6H,hCCl-CCl,
-
+ Cb
(pCICaH+)sCC1-CClr
+ HCL
(~C~CGH,)CI~C-CC~,(C~H,C~-~)
d6 '
Directions for these operations sre given in H. L. Fmcm~, 'Zaboratory Manual of Organic Chemistry," John Wiley & Sons, Inc., New York, 1938, p. 124. L. GATTERMANN AND H. WIELAND,"Laboratory Methods of Organic Chemistry," T h e Macmillan Company, New York, 1937, p. 69.
OCTOBER, 1950 Prepare a solution of 5 g. of DDT (Hercules Powder aerosol-grade, m. p. 103-105") in 30 ml. of carhon tetrachloride, add 0.2 ml. (2 drops) of phosphorus trichloride (a chlorination catalyst), and place this solution in the chlorination apparatus (Wilkens-Anderson 4764-CE1) under the hood. Place a 150-watt bulb about 8 to 10 inches from the solution and heat the flask by means of a water bath to about 65'. Connect the chlorine tank to a trap and carefully open the tank by first opening the main valve and then the needle valve until a slow flow of gas comes from the trap. Then connect the trap to the dispersing tube and adjust the needle valve so that chlorine bubbles through the solution a t a moderate rate. The valve is neuer opened when the tank is connected to an apparatus because a sudden surge of gas may break it. The purpose of the trap is to catch any liquid which may suck hack. Pass the gas into the gently refluxing mixture for one hour. If there is visible loss of solvent, stop the chlorination and replace it. Before shutting the tank off, disconnect the trap from the apparatus. Transfer the mixture to an evaporacmg dish, heat on the steam hath until the solvent is removed, and crystallize the residue from 95 per cent alcohol with about 0.1 g. of Norit. The pure tetrachloride melts at 9192". Report the yield, per cent yield, and melting point. For the isomerization, the tetrachloride is placed in a test tube with a thermometer and heated carefully until the molten mixture reaches a temperature of 160". Remove from the burner, immediately add an amount of anhydrous ferric chloride powder (catalyst) the size of a pin-head, and stir slowly with the thermometer. Avoid excess ferric chloride and he sure i t has not been exposed to air any longer than necessaly; i t is extremely hygroscopic. The melt will become dark bluegreen and there may be a rise in temperature. Quickly cool the tube in ice and water. Pulverize the solid product under about 10 ml. of hot carbon tetrachloride, cool, and filter. Crystallize the solid from carhon tetra, chloride in the usual way. The pure symmetrical tetrachloride melts a t 193-194'. Report the yield, per cent yield, and melting point.
The hydrolysis of this tetrachloride to the bemil is very slow, even in mfluxing aqueous acid solution. TO obtain a higher temperature, and thus a greater rate of in a sealed tube at 190hydrolysis, the reaction is demonstrate the use of the 2000. The instructor gas-oxygen blast lamp, the pressure reducing valve on
539
the oxygen tank, and the sealing and opening of a Carius tuhe. After making satisfactory practice seals, obtain a new tuhe, clean and dry it, and place in it 1 g. of the tetrachloride and a solution of 40 ml. of glacial acetic acid, 9 ml. of water, and 1 ml. of concentrated sulfuric acid. It is important to introduce the materials without leaving any on the walls of the tuhe within 6 to 8 inches of the open end. Otherwise, a good seal cannot be made because the glass will become contaminated with carbon particles. Place the tuhe in its metal protective jacket, place in an oil hath (made from a o n e gallon square can with a hole cut in the top and filled with cottonseed oil), and heat the bath on an electric hot plate a t 19&200° for 24 hours, behind a shatterproof glass screen. Allow the oil bath to cool to room temperature and carry the metal tube with the open end pointed away from you over to the blast lamp. Be sure to wear glasses. Do not handle the tuhe while warm. Tilt the tube toward the burner and, by means of a metal rod in the hole in the bottom of the jacket, push about 1.5 inches of the Carius tube into the open and heat it near the tip until the glass softens. If there is any pressure in the tuhe, i t will blow a small hole in the heated area. If there is no pressure, the seal will remain intact. After this step it is ssfe to remove the tuhe, file a scratch just below the seal, open the tuhe, and transfer the mixture to a small Buchner funnel. (Ordinarily, no pressure mill be found in the tubes in this experiment, but it is exceedingly hazardous to omit this test for pressure.) Wash the yellow solid product well with water, dry, and crystallize once from a mixture of carbon tetrachloride (good solvent) and absolute ethanol (poor solvent). Pure p,pf-dichlorohenzil melts a t 198-199'. Report the yield, melting point, and hand in the product. Also, hand in any surplus 1,2-di-(p-chlorophenyl)-l,1,2,2-tetrachloroethane. HEXAPHENYLBENZENE
Hexaphenylbenzene is made by the condensation of tetraphenylcyclopentadienone (tetracyclone) with stilbene followed by elimination of the endocarbonyl group and dehydrogenation of the hexaphenyldihydrobeneene with bromine?
IThis preparation was developed by Dr. Ralph Stickle, Carbide and Carbon Chemicals Corp., South Charleston, West Virginia, and Dr. Robert Vance, Sherwin-Williams Co., Chicago, Illinois from an example given by W. Dilthey in G e r m Patent No. 631,854, July 4, 1936, and from the preparation of tetraphenylphthalic anhydride (GRUMMI~, O., O T ~ Sw., . 23, 93 (1943)).
JOURNAL OF CHEMICAL EDUCATION
A finely powdered mixture of 3.6 g. of tetracyclone (8) and 2.5 g. of stilbene (Eastman Kodak, m. p. 121-
122") is heated in a sealed Carius tube at 250" (in the electric Carius furnace) for eight hours. The crude product, 5.7 g. melting at 120-16O0, is extracted with 140 ml. of 95 per cent ethanol by boiling the mixture, cooling, and filtering. This removal of unreacted tetracyclone and stilbene leaves 4.6 g., 91.5 per cent of the theoretical yield, melting at 170-174°. Additional extractions will raise the melting point of the hexaphenyldihydrobenzeneto 179.5-180.0".3 To a solution of 1.0 g. of hexaphenyldihydrohenzene in 10 ml. of hromobenzene is added a solution of 0.6 g. This melting point checks Dilthey's wlue given in German Patent No. 631,854. Since a quantitative analysis was not given, the 179.Fr180.0" product was analyzed. Calcd. for C.H,?: C, 93.99; H, 6.01. Found: C, 94.27; H, 5.61.
of bromine in 20 ml. of bromobensene. After refluxing under the hood for three hours, during which time hydrogen bromide is evolved, the mixture is cooled to 0 to loo, filtered, and the crude product washed with several portions of 95 per cent ethanol. Report the yield, per cent yield, and melting point. The high melting range of this product, 421425', requires the use of a metal block type of melting-point apparatus and a thermocouple. Pure hexaphenylbenzene melts at 425426"(4). It is insoluble in most organic liquids, but it can be crystallized from nitrobenzene. LITERATURE CITED (1) GRUMMIT~, O., A. BUCK,AND A. JENKINS, J. Am. C h m . Sac., 67, 155 (1945). (2) WALTON,W. L., ibid., 69, 1544 (1947). (3) JOHNSON, J. R.,AND 0.GRUMMIT~, Or& Sp.,23,92 (1943). W., AND G. HURTIG,Bm., 67B,495, 2004 (1934). (4) DILTHEY,
