Production of Chloro-5-hydroxy-2-nitrobenzoic Acid through Chlorination of 3-Methyl-4-nitrophenol, a Typical Hydrolysate of Fenitrothion

Abstract

Fenitrothion [O, O-dimethyl O-(3-methyl-4-nitrophenyl)phosphorothioate], a typical organophosphorus pesticide, is widely used as an insecticide in Japan. In this study, 3-methyl-4-nitrophenol (3M4NP), which is a typical hydrolysate of fenitrothion, was focused as a possible mutagen precursor because it is reported as a common contaminant in raw water for water works, and is capable of forming mutagens when it is chlorinated in water works. In order to examine molecular formulae of mutagens produced from 3M4NP, a chlorinated 3M4NP sample was analyzed with a high-resolution LC/MS. Several peaks were found in a base peak chromatogram. A peak of m/z 215.971 was focused to be analyzed, suggesting a formation of C₇H₄O₅NCl (mass error = 0.397 mmu or 1.837 ppm). To examine the chemical structure of the found substance, MS² experiments were conducted with a collision induced disassociation technique. Four product ions: m/z 198.9679, 187.9757, 170.9731 and 136.0043 which can be attributed to losses of OH, CO, COOH and Cl functional groups were observed. From these fragment ions and the structure of 3M4NP, the substance was extrapolated to be chloro-5-hydroxy-2-nitrobenzoic acid (C5H2NB). The mutagen formation potential (MFP) of 5-hydroxy-2-nitrobenzoic acid, which is considered to be a precursor of C5H2NB, was tested and the MFP of 3,400 net rev./μmol was observed.