Formation of Aromatic Carboxylic Acids The Kolbe-Schmitt Synthesis

Formation of Aromatic Carboxylic Acids The Kolbe-Schmitt Synthesis 

---

Synthesis of salicylic acid by the Kolbe-Schmitt process (see above) is an example for the direct carboxylation of aromatics.34 At the same time, it is also an example for the limitations of such reactions. Formal insertion of C02 into a C-H bond can usually be achieved with compounds containing active hydrogens (such as phenolates), and perhaps more importantly, the product carboxylic acids have to be stabilized by salt formation. Liberation of the free acid from such carboxylates requires a mineral acid and produces 1 equiv of inorganic salt (waste) (Scheme 6.1). 

---