Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand, Equipe Photochimie, BP 10448, F-63000 Clermont-Ferrand, France.
Photochem Photobiol Sci. 2013 Dec;12(12):2076-83. doi: 10.1039/c3pp50241d.
Azoxystrobin is a systemic fungicide that has a tendency to accumulate at the surface of crop leaves or inside their cuticle where it undergoes photodegradation. Its photochemistry was investigated in n-heptane and isopropanol to mimic the polarity of wax leaves. Using analytical and kinetic data, we demonstrate that azoxystrobin (isomer E) undergoes efficient photoisomerization into the isomer Z with a quantum yield of 0.75 ± 0.08. This value is 30-fold higher than that reported in aqueous solution. The photoisomerization of isomer Z into azoxystrobin is more efficient with a chemical yield of 0.95 ± 0.1. In addition, a pseudo photostationary equilibrium is reached when the ratio [azoxystrobin]/[isomer Z] is 2.0 ± 0.1. Photodegradation also takes place from azoxystrobin (quantum yield = 0.073 ± 0.008). Photoproducts mainly arise from bond cleavage between rings and from demethylation of the ether with or without saturation of the acrylate double bond. Theoretical calculations were undertaken to investigate the photoisomerization mechanism and the solvent effect. These data show that the photochemical reactivity of azoxystrobin is enhanced when the solvent polarity decreases and thus should be significant in leaf waxes.
唑菌酯是一种内吸性杀菌剂，具有在作物叶片表面或角质层内积累的趋势，在那里它会经历光降解。在正庚烷和异丙醇中研究了其光化学性质，以模拟蜡叶的极性。利用分析和动力学数据，我们证明唑菌酯（异构体 E）会有效地异构化为异构体 Z，量子产率为 0.75±0.08。这个值比在水溶液中报道的要高 30 倍。异构体 Z 异构化为唑菌酯的光化学产率更高，化学产率为 0.95±0.1。此外，当[唑菌酯]/[异构体 Z]的比值为 2.0±0.1 时，达到了准光稳态平衡。唑菌酯也会发生光降解（量子产率=0.073±0.008）。光降解产物主要来自于环之间的键断裂以及醚的去甲基化，同时可能会使丙烯酰双键饱和或不饱和。进行了理论计算以研究光异构化机制和溶剂效应。这些数据表明，当溶剂极性降低时，唑菌酯的光化学反应性增强，因此在叶蜡中应该具有重要意义。
