(1) When an alkyl halide is treated with metallic sodium in dry ether, the corresponding higher alkane is formed.
This is called Wurtz reaction or Wurtz coupling reaction.
(2) In this reaction the alkyl radicals from two molecules of the reacting alkyl halide combine or couple to form the higher alkane.
(3) Thus, methyl bromide reacts with sodium in ether to form ethane (C2H6), while ethyl bromide under the same conditions forms n-butane (C4H10).
(4) If a mixture of two different alkyl halides is treated with Na in dry ether, then a mixture of alkanes is obtained called self coupling products.
For example,
A mixture of CH3Br and C2H5Br gives propane along with C2H6 and C4H10.