Mechanism of the Kolbe-Schmitt reaction. Structure of the intermediate potassium phenoxide-CO(2) complex.

Our investigation elucidates the structure of the intermediate in the first stage of the carboxylation reaction of potassium phenoxide. Under the reduced pressure of carbon dioxide the complex is not solvated with the CO(2) molecules. Under the conditions of the carboxylation reaction the potassium phenoxide-carbon dioxide complex is solvated with one or two CO(2) molecules. One of the added CO(2) moieties performs an electrophilic attack on the benzene ring, whereas the old CO(2) moiety becomes a molecule of solvent. Our findings are in good accord with the experimental results obtained by the NMR and IR measurements.