Phosphorous-containing insecticides

The major part of the phosphorus-containing insecticides cannot be considered as organophosphorus compounds in the strict sense because they do not contain a P—C bond. These compounds are esters, amides, anhydrides and fluorides of phosphoric, phosphorothioic and phosphorodithioic acids. Most of them can be classified in one of the types shown in Table 1.2. 

The hydrochloric acid is removed by the strong tertiary base, methyldibutylamine, which has a soluble hydrochloride. In B.P. s 631,549 and 652,981 it was shown that compound (II) could be prepared by the action of dimethylamine on P0C13 in chloroform containing an excess of methylbutylamine. The further reaction with water is very conveniently carried out in the same system by adding an excess of aqueous sodium hydroxide solution. The chloroform layer contains the tertiary amine and (I). The solvent and amine are stripped off leaving the product. Side reactions take place, and the commercial product also contains some triphosphoric pentadimethylamide (I A) and smaller amounts of other phosphoric amides. The compound (I A) is itself also a valuable systemic insecticide. 

An important property of ethers of phosphoric acids is that they can mix with many insecticides, fungicides and acaricides which do not contain phosphorus, while their activity is preserved. These mixtures are used to... 

This subclass contains two sulfur atoms in the phosphoric acid part of the molecule. Mala-thion is a typical phosphorodithioate. It is a safe insecticide controlling household, garden, and greenhouse pests. Malathion has an oral LD30 in rats of 900-5800 mg/kg. 

Because OPs are esters of phosphoric acid or phosphor-othioic acid, they are susceptible to hydrolysis by the A-estcrases. One of the most prominent of the OP insecticides, malathion, contains two carboxylic acid esters and is... 

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