Naturally occurring organophosphorus insecticides

Methyl parathion is an organophosphorus insecticide that is commercially produced in the United States and abroad. Methyl parathion, 0,0-dimethyl 0-(4-nitrophenyl) phosphorothioate, is not known to occur as a natural substance (lARC 1983). It is commercially produced by the reaction of 0,0-dimethyl phos-phorochloridothionate and the sodium salt of 4-nitrophenol in acetone solvent (EPA 1974b HSDB 1999 NIOSH 1976 NRC 1977 Worthing 1979). 

Diazinon is the common name of an organophosphorus insecticide used to control pest insects in soil, on ornamental plants, and on fruit and vegetable field crops. It is also used to control household pests such as flies, fleas, and cockroaches. This chemical is synthetic and does not occur naturally in the environment. Diazinon is sold under common trade names including Alfatox, Basudin, AG 500, Dazzel, Gardentox, and Knoxout. 

Carbamates are sold at a lesser volume than are organophosphorus compounds. The first carbamate (urethane) insecticides were developed in the late 1940s at Geigy Chemical Co. in Switzerland. Research on carbamates was inspired by the known toxicity of the alkaloid physostigmine, which occurs naturally in a West African bean. 

There is a vast chemistry of organophosphorus compounds, and even for arsenic, antimony, and bismuth, the literature is voluminous. Consequently only a few topics can be discussed here. It must also be noted that we discuss only the compounds that have P—C bonds. Many compounds sometimes referred to as organophosphorus compounds that are widely used as insecticides, nerve poisons, and so on, as a result of their anticholinesterase activity, do not, in general, contain P—C bonds. They are usually organic esters of phosphates or thiophosphates examples are the well-known malathion and parathion, (EtO)2Pv(S)(0C6H4NO2). Compounds with P—C bonds are almost entirely synthetic, though a few rare examples occur in Nature. 

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