P p DDT

OH I

CCl3CH 3+

The p,p'-isomer shown in reaction (8-31) is not the only reaction product. Appreciable amounts of o,p'- and o,o'-DDT are also obtained. This synthetic approach has been applied for the preparation of a great variety of DDT analogues. One important example, methoxychlor, is used in place of DDT in many applications because it is biodegradable.

CH3O

CCl3CHO

CH3O-

-OCH3

Methoxychlc h

Methoxychlor in less effective as an insecticide, however, and about three times as costly to prepare, since anisole (methoxybenzene) is a more expensive starting material than chlorobenzene. The estimated LD50 (lethal dose for 50% of the population) of methoxychlor in rats is 5000-7000 mg/kg (VS 250-500mg/kg for DDT).

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