Reaction kinetics and mechanismsof organosilicon fungicide flusilazole with sulfate and hydroxyl radicals

Abstract

[EN] Flusilazole is an organosilane fungicide used for treatments in agriculture and horticulture for control of diseases. The reaction kinetics and mechanism of flusilazole with sulfate and hydroxyl radicals were studied. The rate constant of the radicals with the fungicide were determined by laser flash photolysis of peroxodisulfate and hydrogen peroxide. The results were 2.0 x 10(9) s(-1)M(-1) for the reaction of the fungicide with HO center dot and 4.6 x 10(8) s(-1) M-1 for the same reaction with SO4 center dot- radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S2O82- with flusilazole, were identified as alpha-aminoallcyl and siloxyl radicals and agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. In the continuous photolysis experiments, performed by photo-Fenton reaction of the fungicide, the main degradation products were: (bis(4-fluorophenyl)-hydroxy-methylsilane) and the non-toxic silicic acid, diethyl bis(trimethylsilyl) ester, in ten and twenty minutes of reaction, respectively. (C) 2017 Published by Elsevier Ltd.