Paraoxon solubility

The rat LD qS are 13, 3.6 (oral) and 21, 6.8 (dermal) mg/kg. Parathion is resistant to aqueous hydrolysis, but is hydroly2ed by alkah to form the noninsecticidal diethjlphosphorothioic acid and -nitrophenol. The time required for 50% hydrolysis is 120 d ia a saturated aqueous solution, or 8 h ia a solution of lime water. At temperatures above 130°C, parathion slowly isomerizes to 0,%diethyl 0-(4-nitrophenyl) phosphorothioate [597-88-6] which is much less stable and less effective as an insecticide. Parathion is readily reduced, eg, by bacillus subtilis ia polluted water and ia the mammalian mmen to nontoxic 0,0-diethyl 0-(4-aminophenyl) phosphorothioate, and is oxidized with difficulty to the highly toxic paraoxon [511-45-5] diethyl 4-nitrophenyl phosphate d 1.268, soluble ia water to 2.4 mg/L), rat oral LD q 1.2 mg/kg. 

Table 6.3 shows penetration rates of four insecticides dimethoate, paraoxon, dieldrin, and DDT, through cockroach cuticle. It is seen that the rates of penetration are inversely related to their partition coefficient in the olive oil-water system. In other words, the compound with the best solubility in water, as indicated by its partition coefficient, moved through the cuticle most rapidly. In this experiment, the insecticides were applied to the cuticle as acetone solutions, and it was suggested by the authors that this may have neutralized or canceled any barrier presented by the epicuticle. Thus, the data indicate the... 

Barril, J., Estevez, J., Escudero, M.A., Cespedes, M.V., Niguez, N., Sogorb, M.A., Monroy, A., Vilanova, E. (1999). Peripheral nerve soluble esterases are spontaneously reactivated after inhibition by paraoxon implications for a new definition of neuropathy target esterase. Chem. Biol. Interact. 119-20 541-50. 

Figure 3. Stability of OPH/Fabric, Assays were performed using paraoxon as substrate and as described in the text (A) Stability of immobilized and soluble OPH at 4° C. (A) RL immobilized OPH (flp WT immobilized OPH (9) Soluble WT OPH, (B) Stability of WT OPH/fabric at room temperature in the presence of stabilizing sugars. Preparations were performed as described in the text. (T) trehalose ( ) cellubiose (V) sorbitol ( ) no additive (O) mannitol.

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