MERCURY(II) ION-PROMOTED HYDROLYSIS OF SOME ORGANOPHOSPHORUS PESTICIDES

The promotion of hydrolysis of some organophosphorus pesticides by mer cury(II) ion was studied. The presence of mercuric chloride at 20 mg l itre-1 increased the initial hydrolysis rates of malathion, fenitrothi on, fenthion and parathion-methyl in pH 5.5 buffer by two to three ord ers of magnitude. The hydrolysis was found to be first order with resp ect to both mercury(II) ion and the pesticide. The main hydrolysis pro duct was 3-methyl-4-nitrophenol for fenitrothion, and 4-nitrophenol fo r parathion-methyl. It is postulated that the reaction involves the fo rmation of a 1:1 complex and a very slow regeneration of the mercury(I I) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pesticide dichlorvos.