Degradação química e fotoquímica do organofosforado paraoxona

• Autor(a) principal: Fernandes, Maria Eduarda Camilo [UNESP]
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/127613
• topic: Química ambiental; Toxicologia ambiental; Pesticidas; Compostos organofosforados

This work aimed to study the degradation of an organophosphorus model, the 4- nitrophenyl diethyl phosphate (paraoxon) through photochemical and chemical reactions. The illegal storing, their high toxicity and degradation methods used in the elimination of pesticides have led to the need to find alternative methods for the degradation thereof. Thus, the study photochemical reactions photosensitized type II were employed and the reactive species, singlet oxygen was produced to degrade paraoxon. In parallel to the experiments, the chemical and computational study was conducted to provide information for a possible explanation of the reactivity of the species analyzed. Through the results of calculations performed was possible to analyze the orbital border, which provided valuable information on the inertia of paraoxon against singlet oxygen, suggesting that inductive and resonance effects in the ring have an important role in the reaction mechanism. Already in chemical studies we used hydroxylamine, a nucleophile alpha like through degradation. The method was efficient and high pH dependence of the reaction medium, where the best results for the reactivity of nucleophiles were found in the pH range from 6.27 to 11.49. Studies with different concentrations of nucleophile does not indicate the direct participation of water in the slow step of the reaction mechanism. The thermodynamics of the reaction process very clearly points to an associative mechanism, probably the type SN2 (P). Correlation parameters between pKa of nucleophiles and speed show that paraoxon is insensitive to basicity of the nucleophile, as attested by Brownsted value equal to 0.02 for common nucleophiles. However it is evident the alpha effect presented by hydroxylamine and hydroxylamine methyl. In the presence of hydroxylamine degradation rates increased about 840 times comparing with its spontaneous hydrolysis