Carbonylation Explained

See also: Protein carbonylation.

In chemistry, carbonylation refers to reactions that introduce carbon monoxide (CO) into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry.[1] The term carbonylation also refers to oxidation of protein side chains.

Organic chemistry

Several industrially useful organic chemicals are prepared by carbonylations, which can be highly selective reactions. Carbonylations produce organic carbonyls, i.e., compounds that contain the functional group such as aldehydes, carboxylic acids and esters .[2] Carbonylations are the basis of many types of reactions, including hydroformylation and Reppe reactions. These reactions require metal catalysts, which bind and activate the CO.[3] These processes involve transition metal acyl complexes as intermediates. Much of this theme was developed by Walter Reppe.

Hydroformylation

See main article: Hydroformylation. Hydroformylation entails the addition of both carbon monoxide and hydrogen to unsaturated organic compounds, usually alkenes. The usual products are aldehydes:

\ce + \longrightarrow \ce\ceThe reaction requires metal catalysts that bind CO, forming intermediate metal carbonyls. Many of the commodity carboxylic acids, i.e. propionic, butyric, valeric, etc, as well as many of the commodity alcohols, i.e. propanol, butanol, amyl alcohol, are derived from aldehydes produced by hydroformylation. In this way, hydroformylation is a gateway from alkenes to oxygenates.

Decarbonylation

Few organic carbonyls undergo spontaneous decarbonylation, but many can be induced to do so with appropriate catalysts. A common transformation involves the conversion of aldehydes to alkanes, usually catalyzed by metal complexes:[4]

\ce\ce \longrightarrow \ce + Few catalysts are highly active or exhibit broad scope.[5]

Acetic acid and acetic anhydride

Large-scale applications of carbonylation are the Monsanto acetic acid process and Cativa process, which convert methanol to acetic acid. In another major industrial process, acetic anhydride is prepared by a related carbonylation of methyl acetate.[6]

Oxidative carbonylation

Dimethyl carbonate and dimethyl oxalate are produced industrially using carbon monoxide and an oxidant, in effect as a source of .

\ce + 2\ \longrightarrow \ce + \ceThe oxidative carbonylation of methanol is catalyzed by copper(I) salts, which form transient carbonyl complexes. For the oxidative carbonylation of alkenes, palladium complexes are used.

Hydrocarboxylation, hydroxycarbonylation, and hydroesterification

In hydrocarboxylation, alkenes and alkynes are the substrates. This method is used to produce propionic acid from ethylene using nickel carbonyl as the catalyst:

Notes and References

  1. 10.1016/j.chempr.2018.11.006 . The Chemistry of CO: Carbonylation . 2019 . Peng . Jin-Bao . Geng . Hui-Qing . Wu . Xiao-Feng . Chem . 5 . 3 . 526–552 .
  2. Arpe, .J.: German: Industrielle organische Chemie: Bedeutende vor- und Zwischenprodukte, 2007, Wiley-VCH-Verlag,
  3. 10.1016/1381-1169(95)00130-1. Beller. Matthias. Cornils, B. . Frohning, C. D. . Kohlpaintner, C. W. . 1995. Progress in hydroformylation and carbonylation. Journal of Molecular Catalysis A: Chemical. 104. 17–85.
  4. Hartwig, J. F. Organotransition Metal Chemistry, from Bonding to Catalysis; University Science Books: New York, 2010.
  5. Kreis, M.; Palmelund, A.; Bunch, L.; Madsen, R., "A General and Convenient Method for the Rhodium-Catalyzed Decarbonylation of Aldehydes", Advanced Synthesis & Catalysis 2006, 348, 2148-2154.
  6. Zoeller, J. R. . Agreda, V. H. . Cook, S. L. . Lafferty, N. L. . Polichnowski, S. W. . Pond, D. M. . Eastman Chemical Company Acetic Anhydride Process . . 1992 . 13 . 73–91 . 10.1016/0920-5861(92)80188-S.