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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 nam ...
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 ...
which is then poisoned with various forms of lead
Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
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 org ...
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 no ...
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, an ...
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 whic ...
) and is named after its inventor Herbert Lindlar
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.
Bi ...
.
Synthesis
Lindlar catalyst is commercially available but may also be prepared by the reduction of palladium chloride in a slurry of calcium carbonate (CaCO3) followed by the addition oflead acetate Lead acetate can refer to:
* Lead subacetate
Basic lead acetate, also known as subacetate of lead, is the inorganic compound with the formula Pb3(OH)4(O2CCH3)2. A white solid, it is one of several lead acetates.
History
Goulard's extract is a s ...
. 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
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula lead, ...
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 ...
. 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 org ...
of alkynes
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\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, an ...
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 whic ...
). 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 ...
or 3,6-dithia-1,8-octanediol enhances its selectivity, preventing formation of alkane
In organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms tha ...
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 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 to give the cis-alkene. For example the hydrogenation of acetylenedicarboxylic acid 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 aci ...
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 fum ...
.
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 dihydro vitamin K1.Fritz Weber, August Rüttimann "Vitamin K" Ullmann's Encyclopedia Of Industrial Chemistry, 2012, Wiley-VCH, Weinheim.
See also
* Rosenmund reduction, 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 ...
, a nickel based catalyst used to hydrogenate alkynes to alkenes.
References
{{Palladium compounds Catalysts Palladium compounds Hydrogenation catalysts