Wurtz reaction is coupling of haloalkanes using sodium metal in solvent like dry ether
\[2R-X + 2Na \rightarrow R-R + 2Na^+X^−\]
The reaction consists of a halogen-metal exchange involving the free radical species R• (in a similar fashion to the formation of a Grignard reagent and then the carbon-carbon bond formation in a nucleophilic substitution reaction.)
One electron from the metal is transferred to the halogen to produce a metal halide and an alkyl radical.
\[R-X + M → R• + M+X−\]
The alkyl radical then accepts an electron from another metal atom to form an alkyl anion and the metal becomes cationic. This intermediate has been isolated in a several cases.
\[R• + M → R−M+\]
The nucleophilic carbon of the alkyl anion then displaces the halide in an SN2 reaction, forming a new carbon-carbon covalent bond.
\[R−M+ + R-X → R-R + M+X−\]