Kolbe-Schmidt reaction

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). 

It occurs with the alkyls, aryls or acetylides of metals more electropositive than magnesium, but including Grignard reagents, and is often carried out by adding a solution of the organometallic compound in an inert solvent to a large excess of powdered, solid C02 it is a particularly useful method for the preparation of acetylenic acids. The Kolbe-Schmidt reaction (p. 291) is another example of carbanion carbonation. 

The somewhat analogous Kolbe-Schmidt reaction involves C02 as the electrophile in attack on powdered sodium phenoxide (64b) ... 

KOH plants, environmental awareness in, 20 634. See also Potassium hydroxide KOH solution, 12 215 meta-Koksowy coal grade (Poland), 6 713t Kolbe-Schmidt reaction, 2 208 of salicylic acid synthesis, 22 7-8 Kolmogoroff microscale, 16 697 Konica Dry Color System, 19 348 Konjac glucomannan, 4 7241... 

Kojic aad [501-30-4] Koji fermentation Kolbii coupling Kolbe Schmidt reaction Kolbii synthesis Kollidon... 

In general a phenol will undergo direct carboxylation of the nucleus when the dry sodium salt is heated under pressure with carbon dioxide (the Kolbe-Schmidt reaction). Addition of the weakly electrophilic carbon dioxide is promoted by electron release from the oxyanionic site. With phenol itself the ultimate product is salicylic acid (o-hydroxybenzoic acid) predominantly ortho attack may be attributable to stabilisation of the transition state through chelation. 

Kolbe-Schmidt reaction. The preparation of salicyclic acid or its derivatives from carbon dioxide and sodium or potassium phenolate. 

The classical Kolbe-Schmidt reaction treats alkali metal phenoxides and carbon dioxide at higher than atmospheric pressure, giving salicylic acid. Hirao and Kato developed several modifications for industrial production ". Recently, phenol phosphate was enzymatically carboxylated, giving p-hydroxybenzoic acid ". As for related reactions, Sartori and coworkers conducted o-carbamoylation of aluminum or boron phenoxides with alkyl isocyanate ", and Adachi and Sugasawa o-cyanated phenols using methyl thioisocyanate in the presence of BCI3 (equation 54). ... 

Kolbe-Schmidt reaction 685-687 Konig-Knorr method 673 K—T analysis 503, 504, 513, 514... 

Another example illustrating the safe operation of micro reactors at elevated temperatures and pressures was reported by Hessel et al. [25], for the industrially relevant Kolbe-Schmidt reaction (Scheme 6.8). Potassium hydrogencarbonate (31) was selected as a raw material as it is cheap and readily available, making it suitable for the industrial-scale preparation of 2,4-dihydroxybenzoic acid (32) water was selected as the reaction solvent as it is inexpensive (100-1000 lh-1). To optimize the continuous flow conditions, the authors employed a stainless-steel capillary reactor and evaluated the effect of pressure for a fixed reaction time of 6.5 min at 120 °C. 

Scheme 6.8 The flow synthesis of 2,4-dihydroxybenzoic acid (32) via the Kolbe—Schmidt reaction of resorcinol (33).

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