hydrocarbonylation

Hydrocarbonylation is a class of chemical reactions in which hydrocarbons react with carbon monoxide (CO) and hydrogen (H2) to incorporate a carbonyl group into the molecule. The most important example is hydroformylation, also known as the oxo process, in which alkenes react with CO and H2 under pressure to yield aldehydes with one extra carbon atom. This functionality allows the straightforward conversion of low-cost alkenes into value-added aldehydes used as precursors for alcohols, acids, and other products.

Industrial hydroformylation is typically conducted with homogeneous transition-metal catalysts, most commonly rhodium- or cobalt-based systems with phosphine or other suitable ligands. Reactions use syngas (a mixture of CO and H2) at elevated pressures and temperatures, often several tens of atmospheres and modest temperatures (roughly 50–150°C, depending on substrate). The mechanism proceeds by migratory insertion of CO into a metal–alkyl bond followed by hydrogenolysis to release the aldehyde. Catalyst design and ligand choice influence regioselectivity, with a tendency to favor linear aldehydes for many catalysts while branched aldehydes are obtained with alternative systems.

Applications and scope: The hydroformylation of propylene provides n-butyraldehyde and isobutyraldehyde, which are used to manufacture detergents, plasticizers, and solvents. Because aldehydes are versatile intermediates, downstream transformations include hydrogenation to primary alcohols and oxidation to acids or esters.

Related reactions include hydroacylation, in which aldehydes add to alkenes to form ketones, and other carbonylation processes that form carboxylic acids or esters via CO incorporation. The hydrocarbonylation field continues to extend to diverse substrates, including alkynes and more complex hydrocarbons, aided by advances in catalysts that improve activity and selectivity.