ketonization

Ketonization is a chemical reaction in organic chemistry that involves the conversion of carboxylic acids into ketones. This process typically requires heat and a catalyst, often a metal oxide such as thorium dioxide, aluminum oxide, or manganese dioxide, or a metal salt like calcium acetate. The reaction involves two molecules of a carboxylic acid reacting to form a ketone, carbon dioxide, and water.

The mechanism of ketonization usually proceeds through the formation of a metal carboxylate intermediate. This intermediate then undergoes decarboxylation and subsequent reaction with another carboxylate molecule to yield the ketone. For example, when acetic acid is heated with a catalyst, it can undergo ketonization to produce acetone. The specific conditions, including temperature and catalyst choice, are important for optimizing the yield and selectivity of the desired ketone.

Ketonization reactions are useful for synthesizing symmetrical ketones from readily available carboxylic acids. Asymmetrical ketones can also be synthesized, though this may require careful control of reaction conditions and the use of mixed carboxylic acids. The reaction is a form of decarboxylative coupling. It is generally applicable to both aliphatic and aromatic carboxylic acids. While historically significant, other methods for ketone synthesis, such as Friedel-Crafts acylation or oxidation of secondary alcohols, are often preferred in modern organic synthesis due to their broader scope and milder conditions.