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研究论文

摘要：在分别用λ>310nm和λ>295nm的紫外光照射下,溴氰菊酯在正己烷中都经历了三元环顺反异构化,α-碳旋光异构化及酯键断裂。λ>295nm时的光解速率是λ>310nm时的6.3倍,但异构化效率只有后者的78％。波长对异构化平衡组成及光解产物分布具有一定的影响。加入苯乙酮为光敏剂时,光解速率有明显的提高。去溴反应仅能在λ>295nm时发生,但苯乙酮的存在,则反应受到抑制。在λ>295nm时,溴氰菊酯在乙腈-水中的光解速率与在正己烷中的基本相同,但异构化的效率和平衡组成却有差异。在纯水中的光解速率远低于在上述两溶剂中的,但加入少量丙酮时,光解明显加快。不论有否丙酮存在,溴氰菊酯在纯水中均不发生异构化反应。鉴定了19个光解产物,并对光解反应的途径进行了讨论。

Abstract：Photolysis of deltamethrin in various solvents under UV light (λ> 310 nm and λ > 295 nm) was studied. In hexane. the reaction went through cis-trans isomerization in the propane ring, recemization at a position in the alcohol moiety, and ester cleavage. The photolysis rate at λ> 295nm was 6.3 times greater than that at λ >310nm. though the isomerization efficiency at λ > 295nm was 22% lower. The photoproduct distribution and the equilibrium composition of the isomers were influenced by UV wavelength. Addition of acetophenone as a sensitizer greatly increased the rates of the isomerization and the photodegradation. Reductive de-bromination occurred only at λ>295nm. and was obviously retarded by acetophenone. The photolysis rate was the same in acetonitrile-water(3:2) as that in hexane, whereas the efficiency and equilibrium composition of isomerization were different. In water, the photolysis rate was much lower than that in the above solvents, and the rate increased rapidly when 2% acetone was added. The isomerization did not take place in water even with the presence of acetone. Nineteen photoproducts were identified and the photochemical pathways were discussed.