Hydrolysis of the Pyrethroid Insecticide Cypermethrin in Aqueous Media

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  • TAKAHASHI Naohiro
    Laboratory of Biochemistry and Toxicology, Takarazuka Research Center, Sumitomo Chemical Co., Ltd.
  • MIKAMI Nobuyoshi
    Laboratory of Biochemistry and Toxicology, Takarazuka Research Center, Sumitomo Chemical Co., Ltd.
  • MATSUDA Tadashi
    Laboratory of Biochemistry and Toxicology, Takarazuka Research Center, Sumitomo Chemical Co., Ltd.
  • MIYAMOTO Junshi
    Laboratory of Biochemistry and Toxicology, Takarazuka Research Center, Sumitomo Chemical Co., Ltd.

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Other Title
  • ピレスロイド系殺虫剤サイパーメスリンの水中における加水分解
  • ピレスロイド系殺虫剤サイパーメスリンの水中における加水分解〔英文〕
  • ピレスロイドケイ サッチュウザイ サイパーメスリン ノ スイチュウ ニ オケル

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Abstract

Hydrolysis of (1R, cis, αRS)- and (1R, trans, αRS)-isomers of Cypermethrin [(RS)-α-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2, 2-dichlorovinyl)-2, 2-dimethylcyclopropanecarboxylate] was studied in buffer solutions at pH 3.0, 7.0 and 11.0, and in natural river and sea water at 15°C, 25°C, 40°C and 55°C under laboratory conditions. For making suitable approximations, the expressions for kA, kN and kB of Eq. (1) were calculated, using values of kH at three pH's. kH=kA[H+]+kN+kB[OH-] (1). The pH-rate profile thus obtained showed that hydrolysis of both isomers proceeded predominantly through neutral (pH independent) and base-catalyzed processes in the regions below pH 5.0 and above pH 7.0, respectively, whereas both reactions occurred between pH 5.0 and 7.0. The trans-isomer was hydrolyzed approximately 1.2-1.7 times faster than the cis-isomer at any pH tested between 25°C and 50°C. The rates of hydrolysis of both isomers in buffer solutions were similar to those in one sample of river and one sample of sea water. The cleavage of the ester linkage proceeded more rapidly than the hydration of the CN group at any pH and temperature tested.

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