Preparation and applications of catalytic magnetic nanoparticles

[摘要] (cont.) The reaction was very efficient. Crosslinking increased the particle size to 200nm and therefore the particles were effectively captured by HGMS. The modified particles significantly accelerated the hydrolysis reaction of PNPA. They were five times more reactive than the amidoxime modified particles based on the same weight of materials. The acetylated particles were only partially regenerated due to the Lossen rearrangement of the acetylated hydroxamic acid groups.During the hydrolysis of OP substrates, including diisopropyl fluorophosphate, methylparaoxon and ethyl-paraoxon, the added a-nucleophiles, 2-PAM and acetohydroxamic acid, only attacked the phosphorus atom to substitute the p-nitrophenol groups in methyland ethyl- paraoxon and the fluoride ions in DFP through second order nucleophilic substitution. Reactions between all three substrates and both nucleophiles yielded the same hydrolysis products as the spontaneous hydrolysis with no detected intermediates, indicating the unstable nature of any intermediates that may be formed. The hydroxamic acid modified particles accelerated the hydrolysis of methyl- and ethyl- paraoxon with relatively modest reactivity. Similar to polyhydroxamic acid, the reactivity was much lower than that of monomeric hydroxamic acid due to the steric hindrance from the polymer chains. The particles lost their reactivity after the reaction due to Lossen rearrangement of the phosphoryl hydroxamic acid.

[发布机构] Massachusetts Institute of Technology