The Koolbe-Schmitt Reaction

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Kolbe-Schmitt Reaction Kira Wall (CHE433) 12-3-14 The Kolbe-Schmitt reaction is named after Hermann Kolbe and Rudolf Schmitt. Schmitt published his research in the Journal fur Pracktische Chemie in 1885 while Kolbe published his research in the Annalen der Chemie und Pharmacie in 1860. The reaction adds a carboxyl group onto the benzene ring of a phenol. The process uses a base carbon dioxide and acid work-up. The original reaction done by Kolbe involved the formation of sodium phenoxide through the evaporation of a molar equivalent mixture of phenol and aqueous sodium hydroxide. The hygroscopic sodium phenoxide is then heated while carbon dioxide gas is passed over the molten salt. The mixture is then further heated to give the dianion of salicylic acid along with carbon dioxide and phenol both of which distill away from the mixture. Under these…show more content…
They found that carbon dioxide needed to be activated to build hydroxybenzoic acids with alkali metal phenoxide. They came to this realization by coordinating the alkali metal with the carbon dioxide. This caused the formation of the MOPh-CO2 complex. As the carboxylation reaction proceeded, a direct carboxylation of the benzene ring with another molecule of carbon dioxide did not take place, instead, the CO2 moiety of the MOPh-CO2 complex performed an electrophilic attack on the benzene ring in the ortho and para positions. It was shown that the intramolecular conversion of the MOPh-CO2 complex was the most responsible for the products distribution of the Kolbe-Schmitt reaction. It was observed that the mechanism of the carboxylation reaction of lithium phenoxide was significantly different from those of other alkali metal phenoxides however, there was a resemblance between the mechanisms of the carboxylation reactions of lithium phenoxides and sodium

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