AGRO 56 |
| All pyrethroids are chiral compounds and isomerization has been frequently observed from exposure to heat, sunlight or certain solvents. However, so far isomerization of pyrethroids has not been characterized at the enantiomer level. In this study, we evaluated the occurrence of enantiomerization of permethrin and cypermethrin in various organic solvents and solvent-water systems. The four stereoisomers of permethrin were stable under all test conditions. Rapid enantiomerization of cypermethrin was observed in isopropanol and methanol. After 4 d at room temperature, 18-39% conversions occurred for the different cypermethrin stereoisomers in isopropanol and methanol, and the enantiomerization invariably took place at the Ą carbon position. The enantiomerization was temperature dependent, and was also influenced by water as a co-solvent. Results from this study suggest that exposure to certain solvents and water may cause artifacts in chiral analysis and that for enantiomer-enriched pyrethroid products, such abiotic enantiomerization may render the products less effective. |
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New Developments and Issues in Agrochemical Sciences
8:00 AM-11:00 AM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Poster
Sci-Mix
Division of Agrochemicals |