Organophosphates phosphorothioates

Diethyl 0-(3-methyl-5-pyrazolyl) phosphate (722) and 0,0-diethyl 0-(3-methyl-5-pyrazolyl) phosphorothioate (723) were prepared in 1956 by Geigy and they act, as do all organophosphates in both insects and mammals, by irreversible inhibition of acetylcholinesterase in the cholinergic synapses. Interaction of acetylcholine with the postsyn-aptic receptor is therefore greatly potentiated. 0-Ethyl-5-n-propyl-0-(l-substituted pyrazol-4-yl)(thiono)thiolphosphoric acid esters have been patented as pesticides (82USP4315008). 

Phosphinates are a class of organophosphorus compounds, the metabolism of which has received less attention than that of phosphates (see above) or phosphorothioates and P-halidc compounds (see below). Many phosphinates are rapid but transient inhibitors of acetylcholinesterase and carboxyl-esterases. And like organophosphates and phosphonates, phosphinates are substrates of arylesterases (EC 3.1.1.2). This is exemplified by 4-nitrophen-yl ethyl(phenyl)phosphinate (9.62), whose (-)-enantiomer was hydrolyzed by rabbit serum arylesterase almost 10 times faster than the (+)-enantiomer [133],... 

The Increase in LD q was highest for the chlorinated insecticide, endrln (200%), followed by the organophosphate Insecticide, Cyolane (154%), the phosphorothioate insecticide leptophos (123%), and the carbamate insecticide, Zectran (87%). 

The application of fluorogenic labeling to the determination of some organophosphate insecticides has been attempted [178,179]. Fenthion (0,0-dimethyl 0-[(4-metiiylthio)-m-tolyl] phosphorothioate), Ruelene (0-2-chloro-4-ferf.-butylphenyl O-methyl methyl-phosphoramidate), GC 6506 [dimethyl p-(methylthio)phenyl phosphate] and several other compounds which yield phenols on hydrolysis have been examined. The limits of detection for some of these labeled derivatives have been reported to be in the low nanogram range. The organophosphate Proban [0,0-dimethyl 0-(p-sulphamoylphenyl) phosphorothioate] has been determined directly without hydrolysis by dansylation of the free amino group of the molecule [180]. The derivative exhibited blue fluorescence, as compared to yellow for phenol and alkylamine dansyl derivatives. 

Chlorpyrifos or 0,0-diethyl 0 - 3,5,6- trichloro- 2 -pyridyl phosphorothioate Organophosphate Cholinesterase inhibitor, nonsystemic contact, stomach and respiratory action Control of soil-dwelling and foliar feeding insecticides in fruits and vegetables, also noncrop uses 11-18... 

Fenitrothion, an organophosphate/contact insecticide, is chemically known as 0,0-dimethyl 0-(4-nitro-m-tolyl) phosphorothio-ate, or 0-0-dimethyl-0-3-methyl-4-nitrophenol phospherothioate. 

Moretto, A., Bertolazzi, M., Lotti, M., The phosphorothioic acid 0-(2-chloro-2,3,3-trifluorocyclobutyl) O-ethyl S-propyl ester exacerbates organophosphate polyneuropathy without inhibition ofneuropathy target esterase, Toxicol. Appl. Pharmacol., 129(1), 133-137,1994. 

Organophosphate pesticides are synthetic and are usually esters, amides, or thiol derivatives of phosphoric, phosphonic, phosphorothioic, or phosphonothioic acids. Over 100 organo phosphorus compounds, representing a variety of chemical, physical, and biological properties, are currently on the market (Table 23.1). 

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