Organophosphorus pesticides dimethoate

Organophosphorus pesticides are another example of nonionic, moderately polar compounds (Fig. 7.13). These pesticides are commonly used today and include compounds such as methyl parathion, parathion, diazinon, and dimethoate. They are used as insecticides on crops such as cotton, as fungicides on fruits, and as nematocides on soil. They are moderately polar... 

Detoxification of organophosphorus pesticides before they can reach their target sites is probably the main reason for poor correlation between carcinogenicity and electrophilicity/mutagenicity. The problem is further complicated by the fact that several different enzymes are involved in the metabolic detoxification of organophosphorus pesticides. For example, paraoxon, tetrachlojTvinphos and dimethoate are preferentially detoxified by A-esterase (paraoxonase), GSH-dependent S-alkyltransferase and carboxyesterase (aliesterase), respectively whereas chlorfenvinphos is mainly detoxified by NADPH-dependent oxidative dealkylation... 

Organophosphorus pesticides Acephate , Azinphos-methyl , Chlorpyrifos , Chlorpyriphos-methyl , Diazinon , Dichlorvos (DDVP), Dicrotophos , Dimethoate , Disulfoton , Ethoprop , Eenamiphos , Eenitrothion , Fenthion , Fosthiazate , Malathion , Methamidophos , Methidathion , Methyl-parathion , Mevinphos , Naled , Oxydemeton-methyl , Para-thion , Phorate , Phosalone , Phosmet , Pirimiphos-methyl , Profenofos , Terbufos , Tetrachlorvinphos , Trichlorfon . 

The second group, persistent pesticides, includes certain triazine herbicide derivatives, 2,4-dichlorophenoxycarbonic acids, and others (Buslovich 1986, Popovich and Burkatskaya 1986). Moderately persistent pesticides, the third class, include some systemic organophosphorus pesticides (such as demeton, demeton-methyl, Ekatin, and dimethoate), many synthetic pyrethroids, carbamates, and others. Examples of the fourth division, slightly persistent pesticides, are certain contact organophosphorus chemicals like parathion, methyl-para-thion, and others (Kagan 1977, 1981). 

The organophosphorus pesticides oxydemeton-methyl, trichlorfon, dimethoate, dichlorvos, demeton-j-methyl, fenitrooxon, and fenamiphos (and two metabolites)... 

The reagent sequence is specific for endosulfan and phosphamidon. Other insecticides, e.g. organochlorine insecticides, such as endrin, aldrin, dieldrin, DDT and BHC, organophosphorus insecticides, such as malathion, parathion, dimethoate, quinalphos, phorate and fenitrothion, or carbamate insecticides, such as baygon, car-baryl and carbofuran do not react. Neither is there interference from amino acids, peptides or proteins which might be extracted from the biological material together with the pesticides. 

Malathion is a widely used member of a class of pesticides known as organophospate derivatives. It is biodegradable and less toxic (LDg for female rats is 1000 mg/kg) than DDT. Several other organophosphorus compounds are modifications of this basic structure. They include dimethoate (LD = 387 mg/kg), chlorpyrifos (LD q = 95-270 mg/kg), and methyl parathion (LD o = 18 -50 mg/kg). These organophosphates often are used in the treatment of many pests that are found on vegetables, or, in the case of methyl parathion, on cotton plants. 

---