Phosphoric parathion-ethyl

Additionally, they observed a second pathway, hydrolysis through dealkylation leading to a secondary ester of phosphoric acid which still contains the p-nitrophenyl moiety, i.e., de-ethyl Parathion (O-clhyl-O-p-nilrophenyl-monothiophosphoric acid) ... 

Chemical/Physical. The reported hydrolysis half-lives at pH 7.4 at 20 and 37.5 °C were 130 and 26.8 d, respectively (Freed et al., 1977). The hydrolysis half-lives of parathion in a sterile 1% ethanol/water solution at 25 °C and pH values of 4.5, 5.0, 6.0, 7.0, and 8.0, were 39, 43, 33, 24, and 15 wk, respectively (Chapman and Cole, 1982). Kollig (1993) reported the following products of hydrolysis 0-ethyl-0-(/i-nitrophenyl)phosphorothioic acid, 0-(/i-nitrophenyl)-phosphorothioic acid, phosphorothioic acid, phosphoric acid, 4-nitrophenol, 0,0-diethyl phosphorothioic acid, 0-ethylphosphorothioic acid, and ethanol. Low concentrations of Ca and Cu will catalyze the hydrolysis of parathion in water (Plastourgou and Hoffman, 1984). 

Parathion-methyl is less toxic to humans than the ethyl homologue. This is in agreement with the general experience that dimethyl phosphoric acid and dimethyl thiophosphoric acid derivatives are less toxic to warm-blooded animals than the... 

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