Polyethyleneglycol-catalysed benzil-benzilic acid rearrangement: a reaction in soluble macromolecular cavities

Abstract

Kinetics of benzil-benzilic acid rearrangement was investigated in the presence of polyethyleneglycols (PEG) at different concentrations. PEG of molecular weights 400 and 6000 were used for the studies. A set of solutions was prepared with varying PEG contents. The rearrangement was carried out in these systems and the rate constants were calculated. The rates surprisingly increased with PEG content instead of decreasing due to the reduced ionic movement in these viscous macromolecular solutions. In the presence of KOH and NaOH, PEG acts as a catalyst for the rearrangement. But in presence of LiOH, an inverse relation was observed between PEG content and the rate of reaction. These observations were explained on the basis of the cation-binding ability of polyethyleneglycols.