The dry distillation of
calcium acetate to give
acetone was reported by
Charles Friedel in 1858 and until
World War I ketonization was the premier commercial method for its production. Ketonic decarboxylation of
propanoic acid over a
manganese(II) oxide catalyst in a
tube furnace affords
3-pentanone.
5-Nonanone, which is potentially of interest as a diesel fuel, can be produced from
valeric acid. Stearone is prepared by heating
magnesium stearate. The processing of
biomass often produces chemicals that are too oxygen-rich. Ketonic decarboxylation is one strategy to shift the C/O ratio.
Metal oxide catalysts Dozens or more metal oxides have been investigated as catalysts for the decarboxylation. Early work focused on the oxides of calcium and thorium. Of commercial interest are related ketonizations using
cerium(IV) oxide and
manganese dioxide on
alumina as the
catalysts. The synthesis of
4-heptanone illustrates the production of the metal carboxylate in situ. Iron powder and butyric acid are converted to iron butyrate. Pyrolysis of that salt gives the ketone.
Intramolecular decarboxylations The intramolecular version of ketonic decarboxylation is often called the
Ružička large-ring synthesis (or
Ružička cyclization),
named for
Lavoslav Ružička who developed the technique from prior methods that could synthesize small cyclic compounds from calcium salts of
dicarboxylic acids. It was the first direct route to cyclic compounds with more than 8 members and was used by Ružička to produce
macrocyclic molecules with up to 34 carbon atoms. One target for such reactions are the naturally occurring fragrances
civetone and
muscone. The method involved dry distillation of dibasic salts of a dicarboxylic acid, such as thorium, cerium, and yttrium salts, mixed with copper powder to improve heat transfer. This method was low-yielding for large ring sizes and was eventually supplanted by various methods using the
high dilution principle. A more conventional example of
intramolecular ketonization is the conversion of
adipic acid to
cyclopentanone with
barium hydroxide. ==References==