Reduction of Parathion induced by Light

Abstract

WHILE investigating the decomposition of parathion (O,O-diethyl-O-p-nitrophenylphosphorothionate) I was able to confirm the findings of Ketelaar¹ on the specific action of Cu²⁺-ions in catalysing the hydrolysis leading to p-nitrophenol. Other metal ions are ineffective, and the catalytic action of copper can be suppressed by various chelating agents². The experiments were carried out at room temperature in a barbiturate milieu at pH 8.0 and lasted for more than four weeks. Change in concentration of parathion with a modified polarographic method was followed, and this permitted the estimation of parathion and simultaneously of the p-nitrophenol formed. In certain instances however, in solutions not containing the catalyst, a significant decrease of the polarographic wave of parathion was observed though the corresponding appearance of p-nitrophenol was not detected. Although in publications dealing with the degradation of parathion⁴ there is no allusion to the possibility of a spontaneous reduction, I have shown it to be induced by light.