Wurtz–Fittig Reaction
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The Wurtz–Fittig reaction is the
chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
of an
aryl halide In organic chemistry, an aryl halide (also known as a haloarene) is an aromatic compound in which one or more hydrogen atoms directly bonded to an aromatic ring are replaced by a halide ion (such as fluorine F''−'', chlorine Cl−1,−3,−5, br ...
,
alkyl halide The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents of hydrogen atom. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalka ...
s, and
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
metal to give substituted aromatic compounds. Following the work of
Charles Adolphe Wurtz Charles Adolphe Wurtz (; 26 November 181710 May 1884) was an Alsatian French chemist. He is best remembered for his decades-long advocacy for the atomic theory and for ideas about the structures of chemical compounds, against the skeptical opinio ...
on the sodium-induced coupling of
alkyl halides The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents of hydrogen atom. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalka ...
(the
Wurtz reaction In organic chemistry, the Wurtz reaction, named after Charles Adolphe Wurtz, is a coupling reaction in which two alkyl halides are treated with sodium metal to form a higher alkane. : 2 R−X + 2 Na → R−R + 2 NaX The reaction is of little val ...
),
Wilhelm Rudolph Fittig Wilhelm Rudolph Fittig (6 December 183519 November 1910) was a German chemist. He discovered the pinacol coupling reaction, mesitylene, diacetyl and biphenyl. Fittig studied the action of sodium on ketones and hydrocarbons. He discovered the Fi ...
extended the approach to the coupling of an alkyl halide with an aryl halide. This modification of the Wurtz reaction is considered a separate process and is named for both scientists. : The reaction works best for forming asymmetrical products if the halide reactants are somehow separate in their relative chemical reactivities. One way to accomplish this is to form the reactants with halogens of different
period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...
s. Typically the alkyl halide is made more reactive than the aryl halide, increasing the probability that the alkyl halide will form the
organosodium Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are co ...
bond first and thus act more effectively as a
nucleophile In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
toward the aryl halide. Typically the reaction is used for the alkylation of aryl halides. With the use of ultrasound sodium reacts with some
aryl halide In organic chemistry, an aryl halide (also known as a haloarene) is an aromatic compound in which one or more hydrogen atoms directly bonded to an aromatic ring are replaced by a halide ion (such as fluorine F''−'', chlorine Cl−1,−3,−5, br ...
s to produce biphenyl compounds.


Mechanism

The mechanism of the Wurtz–Fittig reaction has not been the subject of modern investigations. The process was once proposed to involve the combination of an alkyl and aryl radicals. Another mechanistic proposal invoked the generation of organosodium intermediates. The reaction of sodium and chlorobenzene produces
triphenylene Triphenylene is an organic compound with the formula (C6H4)3. It's a flat polycyclic aromatic hydrocarbon (PAH) that has a highly symmetric and planar structure consists of four fused benzene rings. Triphenylene has delocalized 18-''π''-electron ...
, which supports a role for radicals. A role for organosodium compounds is supported by indirect evidence. For example, addition of carbon dioxide to a mixture of sodium and isobutyl bromide results in the formation of
3-methylbutanoic acid Isovaleric acid, also known as 3-methylbutanoic acid or β-methylbutyric acid, is a branched-chain alkyl carboxylic acid with the chemical formula (CH3)2CHCH2CO2H. It is classified as a short-chain fatty acid. Like other low-molecular-weight car ...
after acid workup.


Use of other metals

The Wurtz–Fittig reaction can be conducted using metals other than sodium. Some examples include potassium, iron, copper, and lithium. When lithium is used, the reaction occurs with appreciable yield only under ultrasound. Ultrasound is known to cleave halogen atoms from aryl and alkyl halides through a free-radical mechanism


Applications

The Wurtz–Fittig reaction has limited applicability, because it is plagued by side reactions including rearrangements and eliminations. The reaction has been applied to the laboratory synthesis of some
organosilicon Organosilicon chemistry is the study of organometallic compounds containing carbon–silicon bonds, to which they are called organosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, f ...
compounds. One example is the conversion of
tetraethyl orthosilicate Tetraethyl orthosilicate, formally named tetraethoxysilane (TEOS), ethyl silicate is the organic chemical compound with the formula Si(OC2H5)4. TEOS is a colorless liquid. It degrades in water. TEOS is the of orthosilicic acid, Si(OH)4. It ...
to the mono-tert-butoxy derivative in 40% yield as summarized in this idealized equation: : Molten sodium was used. Other
organosilicon compound Organosilicon chemistry is the study of organometallic compounds containing carbon–silicon bonds, to which they are called organosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, f ...
s synthesized using the Wurtz–Fittig reaction include silylated
calixarene A calixarene is a macrocycle or cyclic oligomer based on a methylene-linked phenols. With hydrophobic cavities that can hold smaller molecules or ions, calixarenes belong to the class of cavitands known in host–guest chemistry. Nomenclature ...
s and
vinylsilane Vinylsilane refers to an organosilicon compound with chemical formula CH2=CHSiH3. It is a derivative of silane (SiH4). The compound, which is a colorless gas, is mainly of theoretical interest. Substituted vinylsilanes More commonly used than th ...
s.


See also

*
Wurtz reaction In organic chemistry, the Wurtz reaction, named after Charles Adolphe Wurtz, is a coupling reaction in which two alkyl halides are treated with sodium metal to form a higher alkane. : 2 R−X + 2 Na → R−R + 2 NaX The reaction is of little val ...


References

{{DEFAULTSORT:Wurtz-Fittig reaction Carbon-carbon bond forming reactions Substitution reactions Name reactions