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| Lindlar catalyst | |
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| Other names | Palladium on calcium carbonate, poisoned |
| Identifiers | |
| CAS number | [7440-05-3] |
| Properties | |
| Molecular formula | not a compound |
| Appearance | Gray powder |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | none |
| R-phrases | R20 R33 R36 R37 R38 |
| S-phrases | S22 S27 S36 S37 S39 |
| Related compounds | |
| Related compounds | Palladium on carbon |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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A Lindlar catalyst is a heterogeneous catalyst that consists of palladium deposited on calcium carbonate and treated with various forms of lead. The lead additive serves to deactivate the palladium sites. A variety of "catalyst poisons" have been used including lead acetate and lead oxide. The palladium content of the catalyst is usually 5% by weight. The catalyst is used for the hydrogenation of alkynes to alkenes.
As described by its inventor,[1][2] the catalyst is prepared by reduction of palladium chloride in a slurry of calcium carbonate followed by adding lead acetate. By this approach, one obtains a catalyst with a large surface area. Further deactivation of the catalyst with quinoline enhances its selectivity, preventing formation of alkanes. An example of alkyne reduction is the reduction of phenylacetylene to styrene.[1]
Alkyne reduction is stereoselective, occurring via syn addition to give the cis-alkene.[3] The commercial organic synthesis of vitamin A also involves an alkyne reduction with the Lindlar catalyst.
Other heterogeneous catalysts useful for hydrogenation are Adam's Catalyst, Palladium Black, and Raney nickel.
References
- ^ a b Lindlar, H.; Dubuis, R. "Palladium Catalyst for Partial Reduction of Acetylenes" Organic Syntheses, Collected Volume 5, p.880 (1973).http://www.orgsyn.org/orgsyn/pdfs/CV5P0880.pdf
- ^ Lindlar, H. "Ein neuer Katalysator für selektive Hydrierungen"; Helv. Chim. Acta 1952, 35, 446-450, doi:10.1002/hlca.19520350205.
- ^ Overman, L. E.; Brown, M. J.; McCann, S. F. "(Z)-4-(Trimethylsilyl)-3-Buten-1-ol" Organic Syntheses, Collected Volume 8, p.609 (1993). http://www.orgsyn.org/orgsyn/pdfs/CV8P0609.pdf
