Kolbe-Schmitt carbonation

Phadtare, P. G., Doraiswamy, L. K. Kolbe-Schmitt carbonation of 2-naphthol. Confirmation of the mass transfer model and process optimization. Industrial Engineering Chemistry Process Design and Development 1969, 8, 165-173. 

A typical example is the Kolbe-Schmitt carbonation of the sodium salt of / -naphthol in an inert liquid medium in the production of /3-oxynaphthoic acid (commonly known as BON acid), a useful intermediate in the manufacture of dyes and other chemicals. Chlorination of wood pulp suspended in water is another example. 

Kolbe-Schmitt carbonation of -naphthol in an inert medium... 

Kolbe-Schmitt carbonation of /3-naphthol experimental time-conversion... 

Figure 17.11 Validation of the mass transfer model (Equation E17.3.3) for the Kolbe-Schmitt carbonation of /3-naphthol.

Table E12.2.1 Kolbe-Schmitt Carbonation of P-Naphthol Experimental Time-Conversion Data...

The key compound m the synthesis of aspirin salicylic acid is prepared from phe nol by a process discovered m the nineteenth century by the German chemist Hermann Kolbe In the Kolbe synthesis also known as the Kolbe—Schmitt reaction, sodium phen oxide IS heated with carbon dioxide under pressure and the reaction mixture is subse quently acidified to yield salicylic acid... 

Section 24 10 The Kolbe-Schmitt synthesis of salicylic acid is a vital step m the preparation of aspirin Phenols as their sodium salts undergo highly regioselective ortho carboxylation on treatment with carbon dioxide at elevated temperature and pressure... 

Kolbe-Schmitt reaction (Section 24 10) The high pressure re action of the sodium salt of a phenol with carbon dioxide to give an o hydroxybenzoic acid The Kolbe-Schmitt reac tion IS used to prepare salicylic acid in the synthesis of as pinn... 

A large number of salts of sahcyhc acid have been prepared and evaluated for therapeutic or other commercial use. Table 7 hsts those most frequently referenced. Sodium sahcylate has analgesic, antiinflammatory, and antipyretic activities and was used extensively in the sixteenth and seventeenth centuries as a remedy, prepared from natural sources, for arthritis and rheumatism. In the 1990s the salt can be obtained directly from Kolbe-Schmitt carboxylation or by the reaction of sahcyhc acid with either aqueous sodium bicarbonate or sodium carbonate. The resulting mixture is heated until effervescence stops the salt is then isolated by filtration and evaporation to dryness at low temperatures. Generally, the solution must be kept slightly acidic so that a white product is obtained if the mixture is basic, a colored product results. The USP product contains 99.5—100.5% NaC H O (anhydrous). The May 1996 price was 8.15/kg (18). 

Manufacture. Several methods have been described for the preparation of -hydroxyben2oic acid. The commercial technique is similar to that of salicylic acid, ie, Kolbe-Schmitt carboxylation of phenol. The modification includes the use of potassium hydroxide in place of caustic (51). The dried potassium phenate is heated under pressure, 270 kPa (2.7 atm) or more, with dry carbon dioxide at 180—250°C. The potassium salt [16782-08-4] of Nhydroxyben2oic acid forms almost quantitatively and can be converted to free acid by using a mineral acid. 

Carbon dioxide reacts with phenolates 1 to yield salicylate 2 with less reactive mono-phenolates, the application of high pressure may be necessary in order to obtain high yields. This reaction, which is of importance for the large scale synthesis of salicylic acid, is called the Kolbe-Schmitt reaction ... 

The Kolbe-Schmitt reaction is limited to phenol, substituted phenols and certain heteroaromatics. The classical procedure is carried out by application of high pressure using carbon dioxide without solvent yields are often only moderate. In contrast to the minor importance on laboratory scale, the large scale process for the synthesis of salicylic acid is of great importance in the pharmaceutical industry. 

Carboxylation with Carbon Dioxide The Kolbe-Schmitt Reaction... 

Sodium phenoxides can be carboxylated, mostly in the ortho position, by carbon dioxide (the Kolbe-Schmitt reaction). The mechanism is not clearly understood, but... 

Salicylic acid. The preparation of salicylic acid by passing carbon dioxide into dry sodium phenoxide at 170-190° is the classical example of the Kolbe-Schmitt reaction. The latter is a method for introducing a carboxyl group directly into a phenol nucleus. 

Kolbe hydrocarbon synthesis orgchem The production of an alkane by the electrolysis of a water-soluble salt of a carboxylic acid. kol-bo. hT-dro kar-bon, sin-th3-s3s Kolbe-Schmitt synthesis org chem The reaction of carbon dioxide with sodium phenoxide at 125°C to give salicyclic acid. kol-bo shmit, sin-th3-s3s Konowaioff ruie phys chem An empirical rule which states that in the vapor over a liquid mixture there is a higher proportion of that component which, when added to the liquid, raises its vapor pressure, than of other components., k6-n9 va-lof, rul ... 

Example 2, the Marasse modification of the Kolbe-Schmitt reaction uses excess of anhydrous potassium carbonate in place of carbon dioxide ... 

Current Methods. The general outline of the Kolbe-Schmitt reaction, as it is employed in the 1990s, is as follows. In the first step, phenol and hot aqueous caustic are mixed to produce the sodium phenate which is taken to dryness. Next, the phenate and dry carbon dioxide are introduced into the carbonator. Air is excluded to minimize oxidation and the formation of colored compounds. The gas—solid mixture is agitated and heated, first at low temperature, followed by several hours at higher temperatures, to complete the formation of sodium salicylate. Variations of this reaction have been noted in the literature and are still being investigated (10,11). One reported scheme produces salicylic acid or substituted salicylic acids by reaction of a granulated alkali metal salt of the respective phenolic compound with C02 in a fluidized bed at 20—130°C until at least 50—80% of the metal salt has been converted to... 

Carboxylation of aromatic rings with carbon dioxide (Kolbe-Schmitt)... 

The Kolbe-Schmitt reaction produces O- and C-carboxylation through the reaction of carbon dioxide with sodium benzenolate at 125° ... 

The Kolbe-Schmitt reaction is related to enzymatic carboxylations as of D-ribulose 1,5-diphosphate with carbon dioxide, a key step in photosynthesis (Section 20-9). The overall result is C—C bond formation by addition of C02 to an enolate salt or its enamine equivalent. 

Crafts alkylation and acylation (Section 22-4E and 22-4F), the Gattermann-Koch reaction for preparation of aldehydes from arenes and carbon monoxide (Section 22-4F), and the Kolbe-Schmitt, Reimer-Tiemann, and Gattermann reactions for synthesis of acids and aldehydes from arenols (Section 26-1E). 

The use of C02 in chemistry normally requires its interaction with metal centers of catalysts one such example is the Kolbe-Schmitt carboxylation of phenol to produce salicylic acid. The potential of C02 as a raw material in the synthesis of carboxylates, carbonates, or carbamates is rather limited. A future aim is the economically attractive synthesis of carboxylic acids, or optically... 

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