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A Lindlar catalyst is a
Alkyne hydrogenation is 
An example of commercial use is the
A Lindlar catalyst is a heterogeneous
Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...
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 ...
that consists 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 ...
deposited on calcium carbonate or barium sulfate
Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs as the mineral barite, which is the main commercial source of barium and ...
which is then poisoned
A poison can be any substance that is harmful to the body. It can be swallowed, inhaled, injected or absorbed through the skin. Poisoning is the harmful effect that occurs when too much of that substance has been taken. Poisoning is not to ...
with various forms of lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
or sulfur. It is used for the hydrogenation
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...
of alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s to alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic ...
s (i.e. without further reduction into alkanes
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in ...
) and is named after its inventor Herbert Lindlar.
Synthesis
Lindlar catalyst is commercially available but may also be prepared by the reduction ofpalladium 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 ...
in a slurry of calcium carbonate (CaCO3) followed by the addition of lead acetate Lead acetate can refer to:
* Lead subacetate (Basic lead acetate), Pb3(OH)4(CH3COO)2
* Lead(IV) acetate
Lead(IV) acetate or lead tetraacetate is an organometallic compound with chemical formula . It is a colorless solid that is soluble in nonpo ...
. A variety of other "catalyst poisons" have been used, including lead oxide
Lead oxides are a group of inorganic compounds with formulas including lead (Pb) and oxygen (O).
Common lead oxides include:
* Lead(II) oxide, PbO, litharge (red), massicot (yellow)
* Lead(II,IV) oxide
Lead(II,IV) oxide, also called red lead o ...
and quinoline
Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sli ...
. The palladium content of the supported catalyst is usually 5% by weight.
Catalytic properties
The catalyst is used for thehydrogenation
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...
of alkynes
\ce
\ce
Acetylene
\ce
\ce
\ce
Propyne
\ce
\ce
\ce
\ce
1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no ...
to alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic ...
s (i.e. without further reduction into alkanes
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in ...
). The lead serves to deactivate the palladium sites, further deactivation of the catalyst with quinoline
Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sli ...
or 3,6-dithia-1,8-octanediol enhances its selectivity, preventing formation of alkane
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in wh ...
s. Thus if a compound contains a double bond as well as a triple bond, only the triple bond is reduced.
An example being the reduction of phenylacetylene
Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. It exists as a colorless, viscous liquid. In research, it is sometimes used as an analog for acetylene; being a liquid, it is easier to handle than acetylene gas.
Preparation
In ...
to styrene
Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
.
Alkyne hydrogenation is stereospecific
In chemistry, stereospecificity is the property of a reaction mechanism that leads to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one (or a subset) of the stereoisomers."Overlap Con ...
, occurring via syn addition
In organic chemistry, syn- and anti-addition are different ways in which substituent molecules can be added to an alkene or alkyne. The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by refl ...
to give the cis-alkene. For example the hydrogenation of acetylenedicarboxylic acid
Acetylenedicarboxylic acid or butynedioic acid is an organic compound (a dicarboxylic acid) with the formula C4H2O4 or . It is a crystalline solid that is soluble in diethyl ether.
The removal of two protons yields the acetylenedicarboxylate dian ...
using Lindlar catalyst gives maleic acid
Maleic acid or ''cis''-butenedioic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is HO2CCH=CHCO2H. Maleic acid is the ''cis''-isomer of butenedioic acid, whereas fumaric ac ...
rather than fumaric acid
Fumaric acid is an organic compound with the formula HO2CCH=CHCO2H. A white solid, fumaric acid occurs widely in nature. It has a fruit-like taste and has been used as a food additive. Its E number is E297.
The salts and esters are known as fu ...
.
An example of commercial use is the 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 ...
of vitamin A
Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably ...
which involves an alkyne reduction with the Lindlar catalyst. These catalysts are also used in the synthesis of dihydrovitamin K1
Phytomenadione, also known as vitamin K1 or phylloquinone, is a vitamin found in food and used as a dietary supplement. It is on the World Health Organization's List of Essential Medicines.
As a supplement it is used to treat certain bleeding ...
.Fritz Weber, August Rüttimann "Vitamin K" Ullmann's Encyclopedia Of Industrial Chemistry, 2012, Wiley-VCH, Weinheim.
See also
*Rosenmund reduction
The Rosenmund reduction is a hydrogenation process in which an acyl chloride is selectively reduced to an aldehyde. The reaction was named after Karl Wilhelm Rosenmund, who first reported it in 1918.
The reaction, a hydrogenolysis, is catalys ...
, a reduction using palladium on barium sulfate, poisoned with sulfur compounds.
* 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 pre ...
, a nickel based catalyst used to hydrogenate alkynes to alkenes.
References
{{Palladium compounds Catalysts Palladium compounds Hydrogenation catalysts