Question

Which metal is used in Wurtz synthesis:
A. Ba
B. Al
C. Na
D. Fe

Answer 1

Hint: Wurtz synthesis is a coupling reaction between two alkyl halides resulting in the formation of an alkane. The reaction proceeds via a free radical intermediate. A metal that can generate free radicals from alkyl halides is used as the catalyst.

Complete Step by Step Solution:
In the Wurtz reaction, alkyl halides undergo a coupling reaction which results in the formation of an alkane. The alkane is formed out of the alkyl groups of the reactant alkyl halides being attached via a carbon-carbon bond.
This reaction can occur with two different alkyl halide molecules and with two molecules of the same alkyl halide, in which case, the resulting alkane will have twice the number of carbon atoms. The general scheme of this reaction is shown below:

Image: The general scheme of the Wurtz reaction

The first step of the Wurtz reaction involves the formation of an alkyl radical from one of the alkyl halides. For this process to happen, there must be a metal catalyst that can donate a single electron and not become unstable. The metals of Group 1 (alkali metals) are perfect for this purpose because they have only 1 electron in their valence orbitals. When that electron is lost, the alkali metal cations attain a stable noble gas configuration.
The alkali metal used in the Wurtz reaction is sodium (\[Na\]). Shown below is the formation of an alkyl radical by sodium.

Image: Formation of the alkyl radical from an alkyl halide

Thus, option C is correct.

Note: The alkyl halide which gets converted into its radical is decided by the stability of the alkyl radical. It is advised that the student learns about the various factors governing the stability of reactive intermediates.