Haloalkanes and Haloarenes - Result Question 2
####2. Which of the following alkane cannot be made in good yield by Wurtz reaction?
[2020]
(a) 2,3-Dimethylbutane
(b) n-Heptane
(c) n-Butane
(d) n-Hexane
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Solution:
- (b) Wurtz reaction is used to prepare symmetrical alkanes like $R_1-R_1$, as
$ R_1-X+2 Na+X-R_1 \xrightarrow{\text{ Dry ether }} R_1-R_1+2 NaX $
If $R_1$ and $R_2$ are different, then mixture of alkanes may be obtained as
$ \begin{aligned} & R_1-X+2 Na+R_2-X \xrightarrow{\text{ Dry ether }} \\ & R_1-R_1+R_1-R_2+R_2-R_2+2 NaX \end{aligned} $
Hence, $n$-heptane cannot be made in good yield using Wurtz reaction, since it is unsymmetrical alkene.
