karboksüülimine

Karboksüülimine is a chemical reaction where a carboxyl group (COOH) is introduced into an organic molecule. This process typically involves the reaction of a nucleophile, such as an organometallic reagent or a carbanion, with carbon dioxide. Carbon dioxide acts as an electrophile, accepting the electron pair from the nucleophile to form a new carbon-carbon bond and the desired carboxylate anion, which is then protonated to yield the carboxylic acid.

One of the most common methods for carbooxylation is the Grignard reaction. In this reaction, a Grignard reagent (RMgX), which contains a strongly nucleophilic carbon atom, reacts with dry ice (solid carbon dioxide). The Grignard reagent attacks the carbon atom of carbon dioxide, forming a magnesium carboxylate salt. Subsequent acidic workup protonates the carboxylate to produce a carboxylic acid.

Another significant method is the Kolbe-Schmitt reaction, which is used industrially for the production of salicylic acid. This reaction involves the carboxylation of phenol under pressure and at elevated temperatures using carbon dioxide in the presence of a base, typically sodium hydroxide. The phenoxide ion, formed by the deprotonation of phenol, acts as the nucleophile.

Carboxylation is a fundamental reaction in organic synthesis, enabling the formation of carboxylic acids, which are versatile functional groups. These carboxylic acids can then be further transformed into esters, amides, acid halides, and other derivatives, making carboxylation a key step in the synthesis of pharmaceuticals, polymers, and various fine chemicals. The ability to introduce a carboxyl group can significantly alter the properties and reactivity of organic molecules.