The Carboxylation of Phenol Derivatives. VIII.

Abstract

It had been known that the Kolbe-Schmidt reaction for the synthesis of hydroxybenzoic acids from alkali phenoxide and carbon dioxide was inhibited in the presence of water. In the present study, however, the desired reaction was found to occur in an aqueous medium in the presence of alkali carbonates . Thus the effects of the amounts of alkali carbonates, reaction temperatures, reaction times, and the initial pressures of carbon dioxide on the yields of salicylic acid, p-hydroxy benzoic acid, and 4-hydroxyisophthalic acid were investigated. It has also been found that, in an aqueous solution, the hydroxybenzoic acids were thermally unstable. They decompose into phenol, which, in turn, is re-carboxylated to form hydroxybenzoic acids in the presence of alkali carbonates to reach an equilibrium state.