Kolbe-Schmitt reaction


Knoevenagel reaction Knorr pyrrole synthesis. Kolbe>Schmitt reaction Leuckart reaction Mannich reaction  [c.1210]

CARBOXYLATION OF PHENOLS ASPIRIN AND THE KOLBE-SCHMITT REACTION  [c.1006]

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  [c.1006]

Carboxylation of Phenols Aspirin and the Kolbe-Schmitt Reaction  [c.1007]

The Kolbe-Schmitt reaction is an equilibrium process governed by thermodynamic control The position of equilibrium favors formation of the weaker base (salicylate ion) at the expense of the stronger one (phenoxide ion) Thermodynamic control is also responsible for the pronounced bias toward ortho over para substitution Salicylate anion IS a weaker base than p hydroxybenzoate and predominates at equilibrium  [c.1007]

The Kolbe-Schmitt reaction has been applied to the preparation of other o hydroxy benzoic acids Alkyl derivatives of phenol behave very much like phenol itself  [c.1007]

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  [c.1287]

Kolbe Schmidt reaction [ALKYLPHENOLS] (Vol 2)  [c.546]

Alkylphenols undergo a carboxylation reaction known as the Kolbe Schmidt reaction. In the following example, the phenolate anion of /)-nonylphenol (15) reacts with carbon dioxide under pressure. Neutralization generates a sahcyhc acid (16) (10).  [c.60]

CARBOXYLATION OF PHENOLS ASPIRIN AND THE KOLBE-SCHMITT REACTION  [c.1006]

Carboxylation of Phenols Aspirin and the Kolbe-Schmitt Reaction  [c.1007]

The Kolbe-Schmitt reaction is an equilibrium process governed by thermodynamic control. The position of equilibrium favors formation of the weaker base (salicylate ion) at the expense of the stronger one (phenoxide ion). Thermodynamic control is also responsible for the pronounced bias toward ortho over para substitution. Salicylate anion is a weaker base than p-hydroxybenzoate and predominates at equilibrium.  [c.1007]

The Kolbe-Schmitt reaction has been applied to the preparation of other o-hydroxy-benzoic acids. Alkyl derivatives of phenol behave very much like phenol itself.  [c.1007]

Kolbe-Schmitt reaction (Section 24.10) The high-pressure reaction of the sodium salt of a phenol with carbon dioxide to give an o-hydroxybenzoic acid. The Kolbe-Schmitt reaction is used to prepare salicylic acid in the synthesis of aspirin.  [c.1287]

Kolbe-Schmitt Reaction 185  [c.185]

Kolbe-Schmitt Reaction  [c.185]

Kolbe-Schmitt Reaction  [c.186]

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  [c.186]

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.  [c.186]

Esterification. Esters and polyesters comprise the second most important class of adipic acid derivatives, next to polyamides. The acid readily reacts with alcohols to form either the mono- or diester. Although the reaction usually is acid-catalyzed, conversion may be enhanced by removal of water as it is produced. The methyl ester is an industrially important material, because it is a distillable derivative which provides a means of separating or purifying acid mixtures. Recent modifications of adipic acid manufacturing processes have included methanol esterification of the dicarboxyUc acid by-product mixture. Thus glutaric acid [110-94-1] and succinic acid [110-15-6] can be recovered upon hydrolysis, or disposed of as the esters (28). Monomethyl adipate can be electrolyzed as the salt to give dimethyl sebacate [106-79-6] (Kolbe synthesis) (29), an important ten-carbon diacid. Diesters from moderately long-chain (8 or 10 carbon) alcohols are also an important group, finding use as plasticizers, eg, for PVC resins. Table 4 Hsts the boiling points of several representative adipate esters. Reactions with diols (especially ethylene glycol) give polyesters, also important as plasticizers in special apphcations. In another important use of adipate esters, low molecular weight polyesters terminated in hydroxyl groups react with polyisocyanates to give polyurethane resins. Polyurethanes consumed about 4% of adipic acid production in the United States in 1986 (30).  [c.239]

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 minimi2e oxidation and the formation of colored compounds. The gas—sohd mixture is agitated and heated, first at low temperature, followed by several hours at higher temperatures, to complete the formation of sodium sahcylate. Variations of this reaction have been noted in the hterature and are stiU being investigated (10,11). One reported scheme produces sahcyhc acid or substituted sahcyhc acids by reaction of a granulated alkah metal salt of the respective phenohc compound with CO2 in a fiuidi2ed bed at 20—130°C until at least 50—80% of the metal salt has been converted to  [c.286]

The key compound in the synthesis of aspir in, salicylic acid, is prepared from phenol by a process discovered in 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 subsequently acidified to yield salicylic acid  [c.1006]

Liquid Crystal Polyesters. These high performance, high added-value products are derived from aH-aromatic precursors and the raw materials are inevitably more expensive. 4-Hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) are both made by the Kolbe-Schmitt carboxylation reaction (55). In this reaction the soHd potassium phenoxide is heated under pressure with carbon dioxide. A principal process improvement uses an inert hydrocarbon oil as a heat-transfer fluid (56). Using phenol and 2-naphthol, respectively, HBA and HNA are made, although reaction conditions differ. 2-Naphthol can give both the 2,3- and 2,6-isomers depending on the alkah metal and the reaction conditions (57). Other LCP comonomers are 4,4 -dihydroxybiphenyl [92-88-6] hydroquinone [123-31 -9] (HQ), terephthaUc acid, NDA, and 4-acetamidophenol [103-90-2]. The latter is used in minor amounts in certain Hquid crystal polyesteramides, eg, Vectra B [82538-13-4] (58). Hydroquinone is manufactured on a large scale, much of it for photographic chemicals and the synthesis of antioxidants (qv). There are several routes to hydroquinone (see Hydroquinone, resorcinol, and catechol). One is the alkylation of benzene or cumene with propene or 2-propanol in the Hquid phase with a zeoHte catalyst to a mixture of 1,3- and 1,4-diisopropylbenzenes (59). These are separated and air oxidized to the hydroperoxides and decomposed into acetone and either HQ or resorcinol. The acetone can be reduced to 2-propanol and recycled via the alkylation stage (60). The latest process for HQ uses the direct oxidation of phenol with hydrogen peroxide and a strongly acid catalyst, such as trifluoromethanesulfonic acid, to a mixture of HQ and catechol (61). Another process uses a special titanium zeoHte with hydrogen peroxide to achieve the same result (62).  [c.294]

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).  [c.288]

Early Synthesis. Reported by Kolbe in 1859, the synthetic route for preparing the acid was by treating phenol with carbon dioxide in the presence of metallic sodium (6). During this early period, the only practical route for large quantities of sahcyhc acid was the saponification of methyl sahcylate obtained from the leaves of wintergreen or the bark of sweet bitch. The first suitable commercial synthetic process was introduced by Kolbe 15 years later in 1874 and is the route most commonly used in the 1990s. In this process, dry sodium phenate reacts with carbon dioxide under pressure at elevated (180—200°C) temperature (7). There were limitations, however not only was the reaction reversible, but the best possible yield of sahcyhc acid was 50%. An improvement by Schmitt was the control of temperature, and the separation of the reaction into two parts. At lower (120—140°C) temperatures and under pressures of 500—700 kPa (5—7 atm), the absorption of carbon dioxide forms the intermediate phenyl carbonate almost quantitatively (8,9). The sodium phenyl carbonate rearranges predominately to the ortho-isomer. sodium sahcylate (eq. 8).  [c.286]


See pages that mention the term Kolbe-Schmitt reaction : [c.829]   
See chapters in:

Named organic reactions 2nd edition  -> Kolbe-Schmitt reaction


Textbook on organic chemistry (1974) -- [ c.755 , c.764 , c.776 ]

Organic chemistry (0) -- [ c.1006 , c.1007 , c.1008 , c.1017 ]

Named organic reactions 2nd edition (2005) -- [ c.185 ]