Question

Why dry ether medium is needed for the Wurtz reaction?

Answer 1

Wurtz reaction:

• Wurtz reaction is employed for the synthesis of higher alkanes from alkyl halides in the condition of sodium in dry ether.
• It is used for the preparation of alkanes having an even number of carbon atoms.
• The mechanism involves a radical mechanism for cleavage of alkyl and halogen bond and nucleophilic substitution reaction for carbon-carbon bond formation.
• The general form of the Wurtz reaction equation can be written as follows:

$2\mathrm{R}-\mathrm{X}\left(\mathrm{aq}\right)+2\mathrm{Na}\left(\mathrm{s}\right)\stackrel{\mathrm{Dry}\mathrm{ether}}{\to }\mathrm{R}-\mathrm{R}\left(\mathrm{g}\right)+2\mathrm{NaX}\left(\mathrm{aq}\right)$

Role of dry ether in reaction:

• The sodium metal used in the reaction is highly reactive so a suitable solvent must be used that would not react with sodium.
• The alkyl halide also has to dissolve in the solvent.
• The sodium halide generated must be insoluble in a solvent that can easily be removed, whereas the resultant alkane must remain in the solution.
• The reaction medium must be an aprotic solvent due to the reaction condition. Dry ether is an ideal non-polar, aprotic solvent for this.