The Laboratory Preparation of DDT' S . F . DARLING Lawrence College, Appleton, Wisconsin
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50 g. of 20 per cent oleum, 45 g. (0.2 mole) monochlorobenzene, and 34 g. (slightly over 0.1 mole) chloral hydrate. The use of some olenm instead of concentrated sulfuric acid alone permits the use of the more stable and readily available chloral hydrate instead of anhydrous chloral as used by Zeidler and Breckenridge. The mixture is now stirred rapidly enough to keep the materials well dispersed, and a t the end of an hour the DDT should separate as a fine granular solid. During this time the temperature rises to 45'C. The stirring is continued for an additional half hour to complete the reaction. The reaction mixture is now poured with stirring into two liters of a 1: 1 mixture' of ice and water and the solid product which separates is collected on a funnel with suction and washed well with cold water. To remove occluded acid, the crude product is transferred to a beaker containing 500 ml. of boiling water. This causes the DDT to melt. The mixture is stirred well and allowed to cool, whereupon the DDT solidifies. The wash water is removed by decantation and the washing with boiling water is repeated two additional times. In order to insure complete removal of the last traces of acid a little sodium bicarbonate is added to the last wash water, while stirring, until it is neutral to litmus paper. The product is then collected on a suction filter and dried. The yield of the crude product is 50 g., which corresponds to over 70 per cent of the theoretical. The melting point of this crude material is about 90°C., while the melting point of pure DDT is 108°C. The low melting point is caused by the presence of isomers of the pure para compound which can be removed by recrystallization of the crude product from ethyl or propyl alcohol. The pure material separates in fine colorless needles that have a slight odor of fresh apples. A 1 per cent solution of DDT in odorless kerosene sprayed on surfaces of rooms, barns, and other places has been found to be effective in killing flies for as long as six months after treatment, according to experiments PROCEDURE conducted by the Bureau of Entomology.* Solutions To a 500-ml. three-neck round-bottom flask equipped of DDT have been reported to be toxic in contact with with an efficient mechanical stirrer and a thermometer the skin. Extended in powdered talc in a concentraare added successively 350 g. of 95 per cent sulfuric acid, tion of 5 per cent, DDT has proved to be an excellent lousicide and as such is now being used in large quantities by the armed forces. The quantities being consumed are so great that a t present there is none available for civilian use, although this situation may soon 6 B n ~ c ~ p m u J. ~ cR.; ~ , Can. chehcm. Pro& Itid., is, chance because several larne companies have recentlv (1944). a CALL-, JOHN R., C h . & ~ c t Eng., . 51,109-14(1944). started its commercial production. 170
ECENTLY there have appeared numerous popular a r t.d e s m . current magazines and the daily press on a new insecticide, DDT. This publicity was the result of the successful use of powders containing DDT in delousing civilians in Naples and North Africa in the recent military campaigns in these areas and the adoption by the Army of such powders for use as a delousing material. The results of preliminary tests of this material as an insecticide were published by the Department of Agriculture2 in 1944. Since then numerous articles have appeared concerning the insecticidal properties of DDT but there have been few articles on the preparation of this compound. DDT is the common designation of 2,2-bis(p-chloropheny1)-l,l,l-trichloroethane, a compound originally prepared by Zeidlera in 1874. No further mention of the preparation of this compound appears in the literature until 1942 when the description of its preparation was announced in a British patent assigned to the J. R. Geigy A,-G.4 Following this, Breckenridge6described its preparation on a large laboratory scale by a slight modification of the method of Zeidler. A description of a continuous commercial method appeared in October, 1944.8 All of these methods are slight modifications of the original procedure of Zeidler which consisted of stirring anhydrous chloral with monochlorobenzene in a large excess of concentrated sulfuric acid until the condensation took place. The author recently has made several experiments on the laboratory preparation of DDT and has improved the conditions for carrying out the condensation so that the preparation can be performed as a regular experiment in the beginning course in organic chemistry. Since i t is thought that these directions might be of interest to others in charge of laboratory courses in organic chemistry anxious to include the preparation of this interesting compound, ,the procedure is being published in this article. The use of DDT as an iusecticide is covered by many patents issued to the Geigy Company.
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