Relative basicities of cyclic ethers and esters. Chemistry of importance to ring-opening co- and terpolymerization reactions

We have re-evaluated the use of the red-shifted νOD vibrational mode in CH3OD as a result of hydrogen-bonding to various oxygen donor ligands in determining the basicity strengths of such donors. This was accomplished by initially defining the relationship of the analogous vibrational shifts of several amines with respect to the corresponding shift in benzene versus their well-established pKbs in water. The reactivity ratios for terpolymerization processes involving two different epoxides and CO2 catalyzed by binary (salen)MX/onium salt (M = Cr or Co) catalyst systems were determined by a Fineman–Ross analysis, i.e., quantifying the amount of respective monomers in the polymer versus that in the feed during the early stages of the process. These reactivity ratios reflect the tendencies for an epoxide monomer to self-propagate or cross-propagate during the monomer enchainment process. The relative basicities of cyclic ethers were shown to greatly influence the interpretation of these measured reactivity ratios.

Graphical abstractProcess dependent on binding ability of epoxide and rate constant for ring-opening step.Figure optionsDownload full-size imageDownload as PowerPoint slide