palladium on carbon
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|OtherNames = Palladium on carbon, Pd/C, Pd-C
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|CASNo = 7440-05-3
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|Section2 = {{Chembox Properties
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|Appearance = Black powder
|SolubleOther = Aqua regia
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Palladium on carbon, often referred to as Pd/C, is a form of palladium used as a catalyst.{{cite book|last1=Nishimura|first1=Shigeo|title=Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis|date=2001|publisher=Wiley-Interscience|location=New York|isbn=9780471396987|pages=34–38|edition=1st|url=https://books.google.com/books?id=RjZRAAAAMAAJ&q=0471396982}} The metal is supported on activated carbon to maximize its surface area and activity.
Uses
=Hydrogenation=
Palladium on carbon is used for catalytic hydrogenations in organic synthesis. Examples include reductive amination,{{cite journal|last1=Romanelli|first1=Michael G.|last2=Becker|first2=Ernest I.|title=Ethylp-dimethylaminophenylacetate|journal=Organic Syntheses|date=1967|volume=47|page=69|doi=10.15227/orgsyn.047.0069}} carbonyl reduction, nitro compound reduction,{{cite book | first1 = Michael B. | last1 = Smith | first2 = Jerry | last2 = March | title = March's Advanced Organic Chemistry | publisher = John Wiley & Sons | year = 2007 | edition=6th | isbn = 978-0-471-72091-1 | page = 1816}}{{cite journal | journal = Tetrahedron Letters | volume = 25 | issue = 32 | year = 1984 | pages = 3415–3418 | title = A general procedure for mild and rapid reduction of aliphatic and aromatic nitro compounds using ammonium formate as a catalytic hydrogen transfer agent | first1 = Siya | last1 = Ram | first2 = Richard E. | last2 = Ehrenkaufer | doi = 10.1016/S0040-4039(01)91034-2 | hdl = 2027.42/25034 | hdl-access = free}} the reduction of imines and Schiff bases and debenzylation reactions.
=Hydrogenolysis=
Palladium on carbon is a common catalyst for hydrogenolysis. Such reactions are helpful in deprotection strategies. Particularly common substrates for hydrogenolysis are benzyl ethers:{{Cite journal|last1=Smith|first1=Amos B.|last2=Zhu|first2=Wenyu|last3=Shirakami|first3=Shohei|last4=Sfouggatakis|first4=Chris|last5=Doughty|first5=Victoria A.|last6=Bennett|first6=Clay S.|last7=Sakamoto|first7=Yasuharu|date=2003-03-01|title=Total Synthesis of (+)-Spongistatin 1. An Effective Second-Generation Construction of an Advanced EF Wittig Salt, Fragment Union, and Final Elaboration|journal=Organic Letters|volume=5|issue=5|pages=761–764|doi=10.1021/ol034037a|issn=1523-7060|pmid=12605509}}
Other labile substituents are also susceptible to cleavage by this reagent. {{cite journal|doi= 10.15227/orgsyn.051.0082
|title= Dehydroxylation of Phenols; Hydrogenolysis of Phenolic Ethers: Biphenyl
|journal= Organic Syntheses
|year= 1971
|volume= 51
|pages= 82|first1=Walter J. |last1=Musliner|first2=John W. |last2=Gates, Jr
}}
=Coupling reactions=
Palladium on carbon is also used for coupling reactions. Examples include the Suzuki reaction and Stille reaction.{{cite journal|last1=Liebeskind|first1=Lanny S.|last2=Peña-Cabrera|first2=Eduardo|title=Stille couplings catalyzed by palladium-on-carbon with CuI as a co-catalyst: synthesis of 2-(4'-Acetylhenyl)thiophene|journal=Organic Syntheses|date=2000|volume=77|pages=138|doi=10.15227/orgsyn.077.0135}}
Preparation
A solution of palladium chloride and hydrochloric acid is combined with aqueous suspension of activated carbon. The palladium(II) is then reduced by the addition of formaldehyde.{{cite journal|last1=Mozingo|first1=Ralph|title=Palladium catalysts|journal=Organic Syntheses|date=1946|volume=26|pages=77–82|doi=10.15227/orgsyn.026.0077|pmid=20280763}} Palladium loading is typically between 5% and 10%. Often the catalyst mixture is stored moist.