Catalyzing a cycloaddition with molecularly imprinted polymers obtained via immobilized templates

Abstract

Polymeric catalysts to be applied in the Diels–Alder cycloaddition of hexachlorocyclopentadiene and maleic acid have been prepared via molecular imprinting with template molecules immobilized on silica particles. These enzyme mimicking polymers exhibit specific catalytic effects compared to non-imprinted control polymers or polymer-free solutions. It could be demonstrated that the activity of the molecularly imprinted material rises when increasing the temperature. By this means, the reduction of the activation energy (as expected for catalysts) from 63 to 55 kJ mol −1 could be observed. Furthermore, the reaction was characterized based on the Michaelis–Menten model. For the diene compound a Michaelis constant of K M=5.8 mmol l −1 and an effective reaction rate of r max,eff=0.4 μmol l −1 s −1, leading to a reaction rate constant k eff=1.1×10 −3 s −1, were determined.