Photolysis Experiments on Phosmet, an Organophosphorus Insecticide

Abstract

The organophosphorus insecticide phosmet is used in plant protection as well as against parasites on animals. Phosmet showed numerous photoinduced reaction pathways, which first were studied in the presence of model environments for animal fur lipids (e.g., wool wax). The model solvents for saturated and unsaturated lipids were cyclohexane and cyclohexene, whereas methanol and 2-propanol were used as models for primary and secondary alcohol moieties of lipids. The measured degradation rates over an irradiation period of 7 h in all solvents used were very similar (49-55%). The obtained photoproducts generally included phthalimide, N-hydroxymethylphthalimide, and N-methoxymethylphthalimide. Furthermore, depending on the solvent used, additional degradation products were detectable as N-isopropoxy- and N-methylphthalimide in the presence of 2-propanol and cyclohexene, respectively. However, in the presence of cyclohexene, despite the similar turnover, distinctly lower concentrations of photoproducts were found, indicating further still unknown degradation pathways. Irradiations in methanol with increasing percentages of water led to higher degradation rates; however, the products were found to be the same. Irradiation experiments with pure phosmet on silica TLC plates and glass surfaces resulted in degradation rates of 19 and 32%, respectively, after 6 h. The results obtained clearly demonstrate for the first time that the photoinduced degradation of phosmet is strongly dependent on the chemical environment, affecting less the turnover than the photoproducts formed. The results additionally demonstrate the need to investigate the degradation behavior of phosmet on wool and in the presence of wool wax.

Insecticidal activity ofGallesia integrifolia (Phytolaccaceae) essential oil

“…The former contains O,O-dimethyl Sphthalimidomethyl phosphorodithioate (Figure No. 4a), a non-systemic insecticide applied on plants (cotton, fruits, and potatoes) and animals (cattle, pig, sheep, and dog) (Sinderhauf & Schwack, 2003), and the latter contains phosphorodithioic acid, S-(2-chloro-1-phthalimidoethyl) O,O-diethyl ester (Figure No. 4b), a non-systemic fungicide and insecticide for treatment of soil and for controlling insects and mites in fruits and vegetables (Morais et al, 2005).…”

Rainfastness and Residual Activity of Insecticides to Control Japanese Beetle (Coleoptera: Scarabaeidae) in Grapes

“…The rate and pattern of insecticide degradation in the environment varies for different compounds and is inßuenced by several key drivers such as temperature, UV light, plant metabolism, and mircoorganisms (Bertrand and Barceló 1991, Baskaran et al 1999, Burrows et al 2002, Sinderhauf and Schwack 2003, de Urzedo et al 2007. Recent studies in fruit crops have shown that applications of organophosphate insecticides result in primarily surface residues on the fruit and foliage, whereas for neonicotinoid insecticides the portions of residues that penetrate plant tissues provide extended residual activity (Wise et al 2006).…”

Adsorptive Degradation of Phosmet Using Hierarchically Porous Calcium Oxide : An Experimental and Theoretical Study

“…At pH 10 and 11, no absorption bands of phosmet were observed in the UV spectrum of phosmet solution recorded before the addition of CaO. The absorption bands in the UV spectrum of phosmet are due to the pthalimide moiety present in phosmet . A possible explanation for the degradation of phosmet at pH 10 and 11 can be the alkaline hydrolysis of pthalimide moiety in highly basic solutions …”