DDT and Other Chlorinated Aromatic Compounds

Many compounds of chlorine with benzene and related substances have found use in medicine, public health, and agriculture. An outstanding example is DDT, which is used as an insecticide and pediculicide. The amount distributed over the earth in thirty years after its introduction in 1940 is about 3 billion kilograms. Its use is now restricted because of its toxicity to humans, birds, and other animals. 

It is synthesized by the reaction of chloral hydrate, Cl3CCH(OH)2, with chlorobenzene, CeHsCl, in the presence of concentrated sulfuric acid, which favors the reaction through its affinity for water (Section 8-2). 

Another example is hexachlorophene, 2,2-methylene-bis(3,4,6-tri-chlorophenol), with formula 

It is made by reaction of 2 moles of 2,4,5-trichlorophenol with 1 mole of 

When chlorine is passed over phosphorus it reacts with it to form phosphorus trichloride  

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