Photodecomposition of the carbamate pesticide carbofuran: Kinetics and theinfluence of dissolved organic matter

This study examined the photodecomposition of carbofuran, a carbamate pesti cide with high oral toxicity. Rate constants are measured for the pesticide in aqueous solution and in the presence of various samples of dissolved or ganic matter (DOM). Kinetic experiments are monitored with HPLC, while reac tion products are determined using HPLC, GC-MS, and H-1 NMR: mechanisms are proposed far the first three steps of the reaction. It was found that the photodecomposition proceeds via first-order reaction kinetics and that the presence of various DOM samples inhibits the photolysis reaction of carbofu ran. This phenomenon can be correlated to the magnitude of the. binding int eraction between carbofuran and DOM. Finally, techniques such as GC-MS and H-1 NMR are used to identify the photodecomposition products. The first thr ee steps of the reaction are defined. In the first step of the reaction, th e carbamate group is cleaved from the molecule. The furan moiety is opened in the second step producing a substituted catechol with a tert-butyl alcoh ol group as the substituent at the number three carbon. This molecule then undergoes a dehydration reaction to form an alkene side group from the tert -butyl alcohol side group.