Parathion and similar compounds

Schrader (1951, 1963) also synthesized a lot of other derivatives of parathion. Parathion-methyl is of similar toxicity and mode of action but is 

Note This table illustrates the high toxicity of parathion compared with two similar analogues. The insecticidal properties of fenitrothion are approximately similar to those of parathion. 

Of the other older dialkyl-aryl phosphorothionates, fenthion is still widely used. Fenthion has a better residual efficiency than parathion and methyl parathion and is probably less toxic to fish — 0.01 mg/1 at 24 hours exposure results in 100% mortality in mosquitoes (Aedes aegypti), whereas 1 mg/1 does not kill any guppy (Lebistes reticulatus) during 48 hours exposure. 

The above reactions show how fenthion is successively oxidized to the sulfon of the oxon, which is the most toxic metabolite. 

Bromophos and trichloronate were once very popular. They have now been superseded because of the content of trihalogenephenol moiety, which makes it likely that preparations are contaminated with dioxins. 

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