Methanolysis of organophosphorus esters promoted by an M²⁺ catalyst supported on polystyrene-based copolymers

Abstract

The methanolysis of three neutral organophosphorus esters (a phosphonate, a phosphonothioate, and a phosphorothionate) promoted by several polymer-supported Zn(II) or Cu(II) containing catalysts was studied. The catalysts consist of a Zn(II) or Cu(II) complex with 1,5,9-triazacyclododecane or phenanthroline attached to a porous polystyrene resin. In each case, the polymer supported catalyst showed activity at near neutral sspH in methanol (8.38) and ambient temperature and provided accelerations of up to a factor of 2.9 × 106 relative to the background reaction at sspH 9.05. The solid materials could be reused several times and could be reactivated when the activity diminished. Various polymers of different porosity and extent of cross-linking were studied, with the net result being that larger porosities offer the best reactivity for catalyzed methanolysis of these OP species in methanol. This is explained by different parameters including the accessibility to reactive sites, the increase of concentration of catalytic sites on the surface of the polymer, and some cooperative effects between neighboring catalytic groups.Key words: functionalized polymer, metal containing, methanolysis, organophosphorus pesticides and CW agents, catalyst.

Recent Advances in Heterogeneous Catalytic Systems Containing Metal Ions for Phosphate Ester Hydrolysis

“…Variations in strategies may be employed to further enhance the efficiency of the heterogeneous catalysts. One such strategy is through the use of flow systems, in which the supported catalyst is incorporated into a column and the reactant is passed over the support material, offering an opportunity for large‐scale detoxification of contaminated aqueous environments [99] . Another relevant example of a flow system that has been shown to effectively detoxify pesticide‐polluted solutions involves a metalloenzyme, that is, a glycerophosphodiesterase from Enterobacter aerogenes (GpdQ).…”

“…Didier et al. used chloromethylated polystyrene as a matrix due to its suitability for further functionalisation with different ligands [99] . The porosity presented by the material was used as a variable in the analysis of the kinetic activity of the catalysts.…”

“…The type of polymer support may be significant. Unsurprisingly, it was found that, for cross‐linked polyvinylbenzene–polystyrene resins, the reactivities varied with the porosity of the resin, the extent of cross‐linking, and the catalyst loading [99] . Accessibility to the active site, an increase of the concentration of catalytic sites, and their proximity to each other were also found to be important factors for the reactivity of the systems [99] .…”

“…Unsurprisingly, it was found that, for cross‐linked polyvinylbenzene–polystyrene resins, the reactivities varied with the porosity of the resin, the extent of cross‐linking, and the catalyst loading [99] . Accessibility to the active site, an increase of the concentration of catalytic sites, and their proximity to each other were also found to be important factors for the reactivity of the systems [99] . These studies are not always straightforward; in one case, leaching of zinc above pH 8 was reported for the Zn II complex immobilised on a 1 % cross‐linked Merrifield resin [101] and, in another case, a diffusion‐related process and product partitioning were observed for a zinc complex of 1,4,7‐triazacyclononane immobilised on Tentagel (mixed polystyrene–polyethylene glycol) resin, necessitating adaptations to the model kinetics [100] .…”

“…Some data in Tables 1 and 2 deserve additional attention, in particular, those studies with the substrates paraoxon [75] and fenitrothion [99] . The latter is a broad spectrum insecticide, whereas the former is a cholinesterase inhibitor and active metabolite of the insecticide 6 .…”