DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane) was the first modern synthetic insecticide.

• Synthesis: Condensed from Chloral ($CC{l}_{3}CHO$) and two molecules of Chlorobenzene in the presence of concentrated sulfuric acid.
• Properties: Highly effective against mosquitoes (malaria) and lice (typhus).
• Environmental Impact: It is extremely chemically stable and fat-soluble. It undergoes biomagnification in the food chain, leading to thin eggshells in birds and toxicity in fish. It is now banned in many countries.