CATALYTIC CYCLE

A 'catalytic cycle' in chemistry is a concept that appreciates the notion that in a chemical reaction a catalyst is often first consumed and then regenerated in the course of a catalytic reaction sequence thereby elaborating on the classical view that of a catalyst not taking part in the reaction itself. Catalytic cycles are commonplace in biochemistry and organometallic chemistry for example in the Monsanto process, the Wacker process and the Heck reaction.
Often a so-called 'sacrificial catalyst' is also part of the reaction system with the intent purpose of regenerating the ''true'' catalyst in each cycle. As the name implies the sacrificial catalyst is not regenerated and irreversibly consumed. This sacrificial compound is also known as a 'stoichiometric catalyst' when added in stoichiometric quantities compared to the main reactant. Usually the true catalyst is an expensive and complex molecule and added in quantities as small as possible. The stoichiometric catalyst on the other hand should be cheap and abundant.