Chemical Changes of Some Organic Compounds in Chlorinated Water. I. Formation of the p=0 Analogs from the p=s Type of Organophosphorous Pesticides

Abstract

As fundamental studies on chemical changes of organophosphorus pesticides during chlorination of the water, fate of 11 kinds of P=S type and 2 kinds of P=O type pesitcides in the chlorinated water was examined by thin-layer and gas chromatographic methods. Most of these pesticides examined were found to undergo a chemical change in water containing free chlorine as small as 0.1 ppm. Therefore, at a higher concentration of free chlorine, the P=S compounds were easily oxidized to P=O analogs in the water. However, P=O analogs were not detected from Dimethoate and Ethion in the water, while Dipterex, a P=O compound, underwent dehydrochlorination and rearrangement to form DDVP. Among the P=O derivatives formed from P=S compounds, Malaoxon, Paraoxon, and Diazoxon were comparatively stable in the water but Methyl paraoxon, Sumioxon, and Phosvel-oxon were markedly hydrolyzed and formed phenolic compounds in the water. Oxidation of P=O compounds with free chlorine was hardly influenced by the presence of magnesium, calcium and ferric ions less them 1.0 ppm but suppressed by a ferrous ion. © 1976, The Pharmaceutical Society of Japan. All rights reserved.