The cooperative effect in reactions of multifunctional compounds has been probed by monitoring the kinetics of the Michael addition of a dendritic polyamine to acrylate-terminated Au nanoparticles. Comparison of the kinetic data for this reaction with those for model monofunctional compounds showed the absence of any cooperativity. This was tentatively attributed to the high flexibility of the dendrimer and the inability of the system to bring mutually reactive functional groups sufficiently close to each other to achieve the rate enhancement effect. The subsequent reaction, methanolysis of the Michael adduct, was found to follow different mechanistic pathways in model monofunctional compounds and Au nanoparticles: while the model reaction undergoes intramolecular general base catalysis, no anchimeric assistance was observed for the reaction of Au nanoparticles. This difference in reactivity, which was attributed to steric effects, resulted in substantially different product distribution patterns for reactions of Au nanoparticles and model monofunctional compounds.
- SELF-ASSEMBLED MONOLAYERS
- GOLD CLUSTER MOLECULES