Articulo
Reaction kinetics and mechanisms of organosilicon fungicide flusilazole with sulfate and hydroxyl radicals
Autor
Mercado Castro, Donaldo Fabio
Bracco, Larisa L. B.
Arques, Antonio
González, Mónica Cristina
Caregnato, Paula
Institución
Resumen
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 × 10<sup>9</sup> s<sup>-1</sup>M<sup>-1</sup> for the reaction of the fungicide with HO· and 4.6 × 10<sup>8</sup> s<sup>-1</sup> M<sup>-1</sup> for the same reaction with SO<sub>4</sub>·⁻ radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S<sub>2</sub>O2/8⁻ with flusilazole, were identified as α-aminoalkyl 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. Facultad de Ciencias Exactas Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas