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A Lindlar catalyst is a heterogeneous catalyst consisting of palladium deposited on calcium carbonate or barium sulfate then poisoned with various forms of lead or sulfur. It is used for the hydrogenation of alkynes to alkenes (i.e. without further reduction into alkanes). It is named after its inventor Herbert Lindlar, who discovered it in 1952.
Herbert Lindlar-Wilson (15 March 1909 – 27 June 2009), better known as Herbert Lindlar, was a British-Swiss chemist. He is known in particular through the development of his catalyst for hydrogenation , as the Lindlar catalyst bears his name.
The United States Drug Enforcement Administration (DEA) maintains lists regarding the classification of illicit drugs (see DEA Schedules).It also maintains List I of chemicals and List II of chemicals, which contain chemicals that are used to manufacture the controlled substances/illicit drugs.
Homogeneous catalysts are also used in asymmetric synthesis by the hydrogenation of prochiral substrates. An early demonstration of this approach was the Rh-catalyzed hydrogenation of enamides as precursors to the drug L-DOPA. [10] To achieve asymmetric reduction, these catalyst are made chiral by use of chiral diphosphine ligands. [11]
The Mortreux system consists of molybdenum hexacarbonyl resorcinol catalyst system. The phenyl and p-methylphenyl substituents on the alkyne group are scrambled. Metal-catalyzed alkyne metathesis was first described in 1968 by Bailey, et al. The Bailey system utilized a mixture of tungsten and silicon oxides at temperatures as high as 450 °C.
Poisoning refers specifically to chemical deactivation, rather than other mechanisms of catalyst degradation such as thermal decomposition or physical damage. [1] [2] Although usually undesirable, poisoning may be helpful when it results in improved catalyst selectivity (e.g. Lindlar's catalyst).
Phenylacetylene is a prototypical terminal acetylene, undergoing many reactions expected of that functional group. It undergoes semihydrogenation over Lindlar catalyst to give styrene. In the presence of base and copper(II) salts, it undergoes oxidative coupling to give diphenylbutadiyne. [6]
Kartstedt's catalyst is often used in hydrosilylation. Before introduction of platinum catalysts by Speier, hydrosilylation was not practiced widely. A peroxide-catalyzed process was reported in academic literature in 1947, [9] but the introduction of Speier's catalyst (H 2 PtCl 6) was a big breakthrough. Karstedt's catalyst was later