Polymeric amines and their copper(II) complexes: Catalysts for the hydrolysis of organophosphate esters

Catalysis of the solvolysis of organophosphorus esters by polymers of aliphatic amines, imidazole, pyridine, 2,2′‐bipyridine, and their copper(II) complexes was studied using diisopropyl fluorophosphate (DEP) as a model substrate. The polymeric catalysts were synthesized either by (1) derivation of available polymers, including polyethylenimine, polyvinyl amine, polyvinyl alcohol, polystyrene, and poly‐4‐vinylpyridine or (2) by polymerization of functionalized monomers such as 4(5)‐vinylimidazole and 4‐vinyl‐4′‐methyl‐2,2′‐bipyridine. Polymer hydrophilicity was controlled by partial quaternization of amine groups with different alkyl halides. The greatest catalytic activity was exhibited by copper(II) complexes of polymers containing the 2,2′‐bipyridine group. At pH 7.6 and 3.7 × 10−3M, the most active of these catalysts reduced the half‐life of DFP from 800 to 9 min. The rate was largely independent of the pH in the range 6.5–8.5 but was limited by the aqueous solubility of the catalyst. Heterogeneous catalysis by some polymers was observed but was less effective. A Lineweaver‐Burk plot of V0−1 versus [DFP]−1 for a soluble polymeric 2,2′‐bipyridine‐copper(II) catalyst was linear. There was no correlation between catalysis of solvolysis of DFP and the carboxylic ester, p‐nitrophenyl acetate.