- 著者
-
野口 大介
- 出版者
- 技術・教育研究会
- 雑誌
- 技術・教育研究論文誌 = Journal of Technology and Education
- 巻号頁・発行日
- vol.28, no.2, pp.49-58, 2021-12
The Kolbe-Schmitt reaction is well known as a synthetic process for the industrial production of aromatic hydroxy carboxylic acids, and it is widely learned in chemical education. Several mechanistic studies of the reaction have been conducted over a century; however, it is supposed that it has not been determined yet. Therefore, the author overviews the literature focusing on its proposed reaction mechanisms, including experimental and theoretical research. In 1957, five mechanisms were reviewed: (1) metalation of aromatic nucleus, (2) intermediate formation of metal aryl carbonate, (3) direct nuclear carbonation, (4) tautomeric rearrangement, and (5) chelate formation and electrophilic substitution. After that, more intermediates of some complexes were also proposed, and X-ray crystal analyses revealed the structures of metal phenoxides (reactants) and sodium salicylate (product), both pure and/or solvated; however, it appears that the structural data were not used sufficiently to promote the mechanistic studies of the reaction. Recently, experimental studies by Kosugi et al. (Org. Biomol. Chem., 1(5), 817–821 (2003)) claimed that direct carboxylation occurs, and the complex of metal phenoxide combined with carbon dioxide is not the intermediate of the reaction; on the other hand, theoretical calculations did not support those conclusions. Further effort would be required for technological development and chemical education to integrate the accumulated knowledge of the studies of the Kolbe-Schmitt reaction mechanisms in the future.