Methods for the Preparation of l,l,l-Trichloro-2,2-Bis(p-Chlorophenyl)Ethane Commonly Known as DDT' EUGENE L. BAILES Colorado Agriculturnl Ezperiment Station, Fort Collins, Colomdo
l,l,l-Trichloro-2,2-bis(pchloropheny1)ethane was originally prepared by Zeidler (I) in 1874. The compound was practically forgotten until a half century later when it was discovered to have insecticidal properties. In 1942, Brand and Busse-Sundermann (2) prepared this compound, a number of related compounds, and their reduction products. They, also, determined the absorption spectra of some of these compounds. The use of the compound as an insecticide ash created a new interest in the preparation, insecticidal value, and the toxicity of the compound. This article deals with the preparation. The compound can be prepared by heating under a reflux condenser to 122'C., a mixture of 16.65 g. of chloral hydrate, 22.5 g. of chlorobenzene, and 200 ml. of concentrated sulfuric acid, shaking vigorously every 10 minutes until the two layers disappear-about 2l/* to 3 hours. After the two layers disappear the mixture is allowed to stand 12 to 24 hours until crystals form. The equations for the reaction are:
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VV c1 CL
Published with the approval of the director as paper No. 191, Scientific Journal Series, Colorado Agricultural Experiment Station.
After the crystals have formed, the sulfuric acid is removed by filtering through a fritted glass filter. The crystals are washed with water to remove sulfuric acid and then recrystallized from an alcohol-ether mixture containing 25 per cent ether. The melting point of the compound is 105°C. The compound decomposes above its melting point. The compound can also be prepared by heating a mixture of 16.65 g. of chloral hydrate, 22.5 g. of chlorobenzene, and 200 ml. of sulfuric acid in an oil bath, keeping the mixtnre agitated with a heavy-duty mechanical stirrer. The heating is continued for 8 to 10 hours and the temperature must not exceed 105°C. This method has two advantages in that the reflux condenser can he eliminated and after the temperature becomes constant very little attention is required. After the mixture has cooled somewhat, it is poured into a large volume of cold water, stirred thoroughly, and allowed to cool. The mass is washed several times with water to remove sulfuric acid. The product can be purified by recrystallizing from an alcohol-ether mixture. The compound is very soluble in esters, halogen compounds, benzene, cyclohexane, and pyridine. It is moderately soluble in kerosene and slightly soluble in water. LITERATURE CITED
O., Bcr., 7, 1180-81 (1874). (1) ZRIDLER, (2) BRAND, K., am A. Busss-SUNDERMANN, aid.,75B, 1819-29 (1942).
