Question

Explain Wurtz and Fittig reactions by examples.

Hint:

Wurtz $\Rightarrow$ alkane formation (from alkyl halides).
Fittig $\Rightarrow$ biaryl formation (from aryl halides).
Wurtz–Fittig $\Rightarrow$ alkylbenzene formation (from alkyl + aryl halides).

Answer 1

Wurtz Reaction:
This reaction involves the coupling of alkyl halides in presence of sodium metal in dry ether to form higher alkanes.
\[ 2\,R{-}X + 2\,Na \;\xrightarrow[\text{dry ether}]{}\; R{-}R + 2\,NaX \] Example:
\[ 2\,CH_3Cl + 2\,Na \;\longrightarrow\; C_2H_6 + 2\,NaCl \] Product: ethane.
Fittig Reaction:
This is a similar reaction but with aryl halides.
Two aryl halide molecules react with sodium in dry ether to give biaryl compounds.
\[ 2\,Ar{-}X + 2\,Na \;\xrightarrow[\text{dry ether}]{}\; Ar{-}Ar + 2\,NaX \] Example:
\[ 2\,C_6H_5Cl + 2\,Na \;\longrightarrow\; C_6H_5{-}C_6H_5 + 2\,NaCl \] Product: biphenyl.
Note:
A combination of Wurtz and Fittig (Wurtz–Fittig reaction) allows coupling between aryl halides and alkyl halides to form alkylbenzenes.