2. Monsanto process for industrial acetic acid synthesis

It is not possible to describe all the possibilities available and all known catalytic applications, even though they have been the subject of industrial processes of considerable importance. The Ziegler-Natta process, the Wacker process, olefin metathesis and the SHOP process, the Monsanto process, olefin hydrocyanation, hydrogenation including asymmetric hydrogenation, and many others are part of this family that is growing and evolving every day.

Let's describe the Monsanto process, which is currently the only process for the industrial synthesis of acetic acid. Initially, RhI ₃ is reduced by CO in water, giving rise to a square planar complex in which rhodium is in oxidation state I and is surrounded by 16 electrons :