palladium on carbon
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Palladium on carbon, often referred to as Pd/C, is a form of
palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
used as a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
. The metal is supported on
activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area avail ...
to maximize its
surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...
and activity.


Uses


Hydrogenation

Palladium on carbon is used for catalytic
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...
s in
organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
. Examples include
reductive amination Reductive amination (also known as reductive alkylation) is a form of amination that involves the conversion of a carbonyl group to an amine via an intermediate imine. The carbonyl group is most commonly a ketone or an aldehyde. It is considered ...
,
carbonyl reduction In organic chemistry, carbonyl reduction is the organic reduction of any carbonyl group by a reducing agent. Typical carbonyl compounds are ketones, aldehydes, carboxylic acids, esters, and acid halides. Carboxylic acids, esters, and acid halides ...
, nitro compound reduction, the reduction of imines and Schiff bases and debenzylation reactions.


Hydrogenolysis

Palladium on carbon is a common catalyst for
hydrogenolysis Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes lysis (breakdown) by hydrogen.Ralph Connor, Homer Adkins. Hydrogenolysis Of Oxygenated Organic Compounds. J. Am. Chem. Soc. ...
. Such reactions are helpful in deprotection strategies. Particularly common substrate for hydrogenolysis are benzyl ethers: *: Other labile substituents are also susceptible to cleavage by this reagent.


Coupling reactions

Palladium on carbon is also used for
coupling reaction A coupling reaction in organic chemistry is a general term for a variety of reactions where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = ...
s. Examples include the
Suzuki reaction The Suzuki reaction is an organic reaction, classified as a cross-coupling reaction, where the coupling partners are a boronic acid and an organohalide and the catalyst is a palladium(0) complex. It was first published in 1979 by Akira Suzuki, ...
and
Stille reaction The Stille reaction is a chemical reaction widely used in organic synthesis. The reaction involves the coupling of two organic groups, one of which is carried as an organotin compound (also known as organostannanes). A variety of organic electro ...
.


Preparation

A solution of
palladium chloride Palladium(II) chloride, also known as palladium dichloride and palladous chloride, are the chemical compounds with the formula PdCl2. PdCl2 is a common starting material in palladium chemistry – palladium-based catalysts are of particular value ...
and
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...
is combined with
aqueous An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be rep ...
suspension of
activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area avail ...
. The palladium(II) is then reduced by the addition of formaldehyde. Palladium loading is typically between 5% and 10%. Often the catalyst mixture is stored moist.


See also

*
Palladium black Palladium black is a coarse, sponge-like form of elemental palladium which offers a large surface area for catalytic activity. It is used in organic synthesis as a catalyst for hydrogenation reactions. The term palladium black is also used coll ...
*
Platinum on carbon Platinum on carbon, often referred to as Pt/C, is a form of platinum used as a catalyst. The metal is supported on activated carbon in order to maximize its surface area and activity. Uses Catalytic hydrogenation Platinum on carbon is used for ...
*
Platinum dioxide Adams' catalyst, also known as platinum dioxide, is usually represented as platinum(IV) oxide hydrate, PtO2•H2O. It is a catalyst for hydrogenation and hydrogenolysis in organic synthesis. This dark brown powder is commercially available. The ...
*
Rhodium-platinum oxide Rhodium-platinum oxide (Rh–Pt oxide), or Nishimura's catalyst, is an inorganic compound used as a hydrogenation catalyst. Uses Rh–Pt oxide is used to reduce various aromatic compounds to their respective cycloalkanes or saturated heteroc ...
*
Lindlar catalyst A Lindlar catalyst is a heterogeneous catalyst that consists of palladium deposited on calcium carbonate or barium sulfate which is then poisoned with various forms of lead or sulfur. It is used for the hydrogenation of alkynes to alkenes (i.e. ...
* Raney nickel *
Urushibara nickel Urushibara nickel is a nickel based hydrogenation catalyst, named after Yoshiyuki Urushibara. History It was discovered by Yoshiyuki Urushibara in 1951, while doing research on the reduction of estrone to estradiol. Preparation First nickel is pr ...


References

{{reflist Palladium Hydrogenation catalysts