The Solvent Effect on Carboxylation of Potassium Phenoxide

The Carboxylation of Phenol Derivatives. X

Abstract

As continuation of our previous studies, the carboxylation of potassium phenoxide in a liquid state was investigated under higher carbon dioxide pressure. Particularly, attempts have been made to elucidate the effects of the physical and chemical properties of the solvents on the yields and on the isomer distributions of the hydroxy carboxylic acids.
Even in water-insoluble aprotic solvents, the reaction proceeded in a manner similar to that of gas-solid state carboxylation. Apparently, high-boiling solvents, such as biphenyl ether, kerosene, and light oil, etc. improved the yields of the acids. Best solvents were found among water-miscible aprotic-polar solvents, DMF, DMA, NMP, and HMPA. The results were not analogous to that obtained in gassolid state reactions. A few other protonic solvents were also found to be effective.
The yields of the acids show rough correlations with the physical properties of the solvents, but the ratios of the p-isomer/o-isomer do not, except for the above mentioned acid amide solvents.