Influence of Alkali Metal Cations upon the Kolbe−Schmitt Reaction Mechanism

Abstract

The mechanisms of the carboxylations of lithium, potassium, rubidium, and cesium phenoxides are investigated by means of the DFT method with the LANL2DZ basis set. It is shown that the reactions of all alkali metal phenoxides with carbon dioxide occur via very similar reaction mechanisms. The reactions can proceed in the ortho and para positions. The exception is lithium phenoxide which yields only salicylic acid in the Kolbe-Schmitt reaction. It is found that the yield of the para substituted product increases with increasing the ionic radius of the alkali metal used. An explanation for this experimental and theoretical observation is proposed.

Formation of Potassium 2-Hydroxy-6-naphthoate by Kolbe-Schmitt Carboxylation: A Joint Experimental and Theoretical Study

“…These results imply that among three HNA isomers 2,6-HNA is the most favorable product in the carboxylation of K-2-naphthoxide. The product selectivity could be related with the activation mechanism of K-2-naphthoxide in the presence of carbon dioxide and the thermal stability of reaction intermediates of the reaction [2][3][4][5]8]. Fig.…”

“…The Kolbe-Schmitt reaction offers a direct means of CO2 fixation on hydroxy-aromatic compounds, producing aromatic hydroxycarboxylic acids, such as salicylic acid, p-hydroxy-benzoic acid, 2-hydroxy-3-naphthoic acid (2,3-HNA), and 2-hydroxy-6-naphthoic acid (2,6-HNA). The carboxylation reaction of alkali metal phenoxides has been a subject of numerous experimental and theoretical investigations [1][2][3][4][5][6]. The reaction mechanism has been proposed by means of density functional theory (DFT) methods [2][3][4][5][6], and the structure of an intermediate alkali metal phenoxide-CO2 complex has been elucidated [4].…”

“…The carboxylation reaction of alkali metal phenoxides has been a subject of numerous experimental and theoretical investigations [1][2][3][4][5][6]. The reaction mechanism has been proposed by means of density functional theory (DFT) methods [2][3][4][5][6], and the structure of an intermediate alkali metal phenoxide-CO2 complex has been elucidated [4]. It has been shown that the yield of the parasubstituted product increases with increasing ionic radius of the alkali metal used [3,5].…”

“…The reaction mechanism has been proposed by means of density functional theory (DFT) methods [2][3][4][5][6], and the structure of an intermediate alkali metal phenoxide-CO2 complex has been elucidated [4]. It has been shown that the yield of the parasubstituted product increases with increasing ionic radius of the alkali metal used [3,5]. A quantitative explanation for this occurrence and the equilibrium behavior of the Kolbe-Schmitt reaction has been provided [2,3].…”

“…It has been shown that the yield of the parasubstituted product increases with increasing ionic radius of the alkali metal used [3,5]. A quantitative explanation for this occurrence and the equilibrium behavior of the Kolbe-Schmitt reaction has been provided [2,3]. The mechanism was also investigated by using a dimer model [6].…”