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The Wurtz reaction, named after Charles-Adolphe Wurtz
Charles-Adolphe Wurtz

Adolphe Wurtz was a French chemist of German extraction. He is perhaps best remembered by chemists for the Wurtz reaction, to form carbon-carbon bonds by reacting alkyl halides with sodium, and for his discoveries of ethylamine and ethylene glycol....
, is a coupling reaction
Coupling reaction

A coupling reaction in organic chemistry is a catch-all for a range of reactions in Organometallic chemistry where two hydrocarbon free radical are coupled with the aid of a metal containing catalyst....
 in organic chemistry
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
, organometallic chemistry
Organometallic chemistry

Organometallic chemistry is the study of chemical compounds containing chemical bonding between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character....
 and recently inorganic main group polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s, whereby two alkyl
Alkyl

An alkyl is a univalent Radical consisting of carbon and hydrogen atoms, arranged in a chain. The Alkyls form homologous series with the general formula CnH2n+1....
 halides are reacted with sodium
Sodium

Sodium is an element which has the symbol Na , atomic number 11, atomic mass 23 amu , and a common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" ....
 to form a new carbon-carbon bond:

2R-X + 2Na ? R-R + 2Na+X-


The related reaction dealing with aryl halides is called the Wurtz-Fittig reaction
Wurtz-Fittig reaction

The Wurtz-Fittig reaction is the chemical reaction of aryl halides with alkyl halides and sodium metal to give substituted aromatic compounds....
.

R-X + Na ? R• + Na+X-


The alkyl radical then accepts an electron from another sodium atom to form an alkyl anion and the sodium becomes cationic.
R• + Na ? R-Na+


The alkyl anion then displaces the halide in an SN2 reaction, forming a new carbon-carbon covalent bond.
R-Na+ + R-X ? R-R + Na+X-


Example
Here methyl iodide
Iodomethane

Iodomethane, commonly called methyl iodide and commonly abbreviated "MeI", is the Organoiodine compound with the formula CH3I. This Density Vapor pressure liquid is related to methane by replacement of one hydrogen atom by an atom of iodine and its Dipole#Molecular dipoles is 1.59 D....
 and ethyl chloride
Chloromethane

Chloromethane, also called Methyl chloride, R-40 or HCC 40, is a chemical compound of the group of organic compounds called haloalkanes. It was once widely used as a refrigeration....
 are reacted with powdered sodium metal in anhydrous ether.






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The Wurtz reaction, named after Charles-Adolphe Wurtz
Charles-Adolphe Wurtz

Adolphe Wurtz was a French chemist of German extraction. He is perhaps best remembered by chemists for the Wurtz reaction, to form carbon-carbon bonds by reacting alkyl halides with sodium, and for his discoveries of ethylamine and ethylene glycol....
, is a coupling reaction
Coupling reaction

A coupling reaction in organic chemistry is a catch-all for a range of reactions in Organometallic chemistry where two hydrocarbon free radical are coupled with the aid of a metal containing catalyst....
 in organic chemistry
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
, organometallic chemistry
Organometallic chemistry

Organometallic chemistry is the study of chemical compounds containing chemical bonding between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character....
 and recently inorganic main group polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s, whereby two alkyl
Alkyl

An alkyl is a univalent Radical consisting of carbon and hydrogen atoms, arranged in a chain. The Alkyls form homologous series with the general formula CnH2n+1....
 halides are reacted with sodium
Sodium

Sodium is an element which has the symbol Na , atomic number 11, atomic mass 23 amu , and a common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" ....
 to form a new carbon-carbon bond:

2R-X + 2Na ? R-R + 2Na+X-


The related reaction dealing with aryl halides is called the Wurtz-Fittig reaction
Wurtz-Fittig reaction

The Wurtz-Fittig reaction is the chemical reaction of aryl halides with alkyl halides and sodium metal to give substituted aromatic compounds....
.

Mechanism


This reaction involves the radical species R•.

One electron from sodium is transferred to the halogen to produce a sodium halide and an alkyl radical.
R-X + Na ? R• + Na+X-


The alkyl radical then accepts an electron from another sodium atom to form an alkyl anion and the sodium becomes cationic.
R• + Na ? R-Na+


The alkyl anion then displaces the halide in an SN2 reaction, forming a new carbon-carbon covalent bond.
R-Na+ + R-X ? R-R + Na+X-


Example


Wurtz Fittig
Here methyl iodide
Iodomethane

Iodomethane, commonly called methyl iodide and commonly abbreviated "MeI", is the Organoiodine compound with the formula CH3I. This Density Vapor pressure liquid is related to methane by replacement of one hydrogen atom by an atom of iodine and its Dipole#Molecular dipoles is 1.59 D....
 and ethyl chloride
Chloromethane

Chloromethane, also called Methyl chloride, R-40 or HCC 40, is a chemical compound of the group of organic compounds called haloalkanes. It was once widely used as a refrigeration....
 are reacted with powdered sodium metal in anhydrous ether. Alkane
Alkane

Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon and hydrogen , wherein these atoms are linked together exclusively by single bonds without any cyclic structure ....
s containing double the number of carbon atoms are formed, i.e. methyl iodide gives ethane, and ethyl chloride gives n-butane
Butane

Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3....
.

The solvent, ether in this case, must be anhydrous (free of moisture) because the alkyl anions are so basic (the pKa
PKA

PKA or pKa may be:* Protein kinase A, a cAMP activated protein kinase* pKa, the symbol for Acid dissociation constant...
 of the alkyl proton is 48–50) that they readily deprotonate water to hydroxide ion, forming alcohols, and reducing the yield of the desired product.

Limitations


The Wurtz reaction is limited to the synthesis of symmetric alkanes. If two dissimilar alkyl halides are taken as reactants, then the product is a mixture of alkanes that is, often, difficult to separate. Since the reaction involves free radical species, a side reaction also occurs to produce an alkene. This side-reaction becomes more significant when the alkyl halides are bulky at the halogen-attached carbon. This is because the activation energy required for the SN2 reaction in the second step becomes significantly high, so the alternate elimination mechanism is favored.

The Corey-House-Posner-Whitesides reaction
Corey-House-Posner-Whitesides reaction

The Corey-House synthesis is an organic reaction that involves the reaction of a lithium dialkyl cuprate with an alkyl halide to form a new alkane....
 is an alternative route to alkane synthesis that overcomes some of the limitations of the Wurtz reaction.