What is the Wurtz-Fittig Reaction?
The Wurtz-Fittig reaction mechanism can be explained either via the organo-alkali mechanism or the radical mechanism. The chemical reaction of aryl halides with alkyl halides and sodium metal with dry ether present to yield substituted aromatic compounds is called the Wurtz-Fittig reaction for the scientists – Charles Adolphe Wurtz and Wilhelm Rudolph Fittig (Wurtz for the discovery of the carbon-carbon bond formation from the coupling of two alkyl halides and Fittig for extending the approach to alkyl halide – aryl halide coupling). An example of such a reaction is shown below.
If the alkyl halide has more chemical reactivity than the aryl halide, it will form the carbon sodium bond first and act as a nucleophile to the aryl halide, helping the reaction in forming asymmetrical products. If the reactants are formed with halogens of different periods, the difference in reactivity between the alkyl halide and aryl halide can be achieved easily.
Wurtz-Fittig Reaction Mechanism
The Organo Alkali Mechanism
When the aryl halide is reacted with sodium metal, an intermediate organo-alkali compound is formed, which is followed by a nucleophilic attack of the alkyl halide as shown below. Thus, the required alkyl-aryl is formed.
The Radical Mechanism
The sodium atom acts as a moderator for the formation of alkyl radicals and aryl radicals. These alkyl and aryl radicals now combine to form a substituted aromatic compound as shown below.
To conclude, the Wurtz-Fittig Reaction Mechanism can be described either via the radical mechanism or the organo-alkali mechanism, there exists empirical evidence for both. The reaction can also be conducted using metals other than sodium (such as potassium, iron, copper, and lithium). The reaction can also be called a coupling reaction. It requires an aprotic solvent as the reaction medium for which dry ether is quite suitable as it is a good non-polar aprotic solvent.