Insecticidal Action of DDT

Abstract

SINCE the discovery of the outstanding insecticidal activity of 1 : 1 : 1-trichloro-2 : 2-di-(4-chlorophenyl) ethane (DDT), many analogues have been synthesized, and several investigators^1,2 have reached the conclusion that the most toxic are also the most similar to DDT in shape and size. If the toxicity is due to its structural resemblance to some essential insect metabolite or to cholesterol³, then compounds isosteric with DDT ought to act similarly, and replacement of the three (β-chlorine atoms by spatially similar atoms or groups of atoms should not destroy activity. Suitable groups were thought to be —CH₃ (radius 1.7 A.) and —OH (radius 2.0 A.), which conform reasonably well with Cl (radius 1.7 A.)—an agreement which has been shown⁴ to be well within the limits required for isosteric activity in serological reactions.