page_title: Wurtz–Fittig reaction
section_title: Mechanism
hierarchical_section_title: Wurtz–Fittig reaction / Mechanism
caption_attribution_description: English: Radical Mechanism for the Wurtz-Fittig Reaction
context_page_description: The Wurtz–Fittig reaction is the chemical reaction of aryl halides with alkyl halides and sodium metal in the presence of dry ether to give substituted aromatic compounds. Charles Adolphe Wurtz reported what is now known as the Wurtz reaction in 1855, involving the formation of a new carbon-carbon bond by coupling two alkyl halides. Work by Wilhelm Rudolph Fittig in the 1860s 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 periods. Typically the alkyl halide is made more reactive than the aryl halide, increasing the probability that the alkyl halide will form the organosodium bond first and thus act more effectively as a nucleophile toward the aryl halide.
context_section_description: There are two approaches to describing the mechanism of the Wurtz–Fittig reaction. The first involves the sodium-mediated formation of both alkyl and aryl radicals. The alkyl and aryl radicals then combine to form a substituted aromatic compound.
  The second approach involves the formation of an intermediate organo-alkali compound followed by nucleophilic attack of the alkyl halide.
  There is empirical evidence for both approaches. The free radical mechanism is supported by the observation of side products whose formation cannot be explained by an organo-alkali mechanism. In a reaction between sodium and cholorobenzene, Bachmann and Clarke find that one of the many side products is triphenylene. They contend that the only way to explain the formation of triphenylene is through a free radical mechanism.
  The organo-alkali mechanism is supported by indirect evidence which shows that an organo-alkali intermediate actually forms during the reaction. This has been observed my many investigators. For example, Shoruguin shows that bubbling carbon dioxide through a mixture of sodium and isobutyl bromide results in the formation of 3-methylbutanoic acid.
  The formation of 3-methylbutanoic acid follows from a nucleophilic attack of carbon dioxide by an organosodium compound. These results suggest that Wurtz–Fittig reaction occurs via the formation of an organoalkali compound since the reaction conditions are similar.
caption: Radical Mechanism for the Wurtz–Fittig Reaction
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