Write a note on Williamson's ether synthesis.

(N/A) Williamson's ether synthesis is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers.
In this reaction,an alkyl halide is reacted with a sodium alkoxide to form an ether.
The general reaction is: $R-X + R'-O^-Na^+ \rightarrow R-O-R' + NaX$.
This reaction involves an $S_N2$ mechanism.
For the synthesis of unsymmetrical ethers,it is important to choose the reactants such that the alkyl halide is primary $(1^\circ)$ to minimize steric hindrance and favor the $S_N2$ pathway.
If a tertiary alkyl halide is used,elimination (forming an alkene) becomes the major reaction instead of substitution.
Example: The reaction of sodium tert-butoxide with methyl bromide yields tert-butyl methyl ether: $(CH_3)_3C-O^-Na^+ + CH_3-Br \rightarrow (CH_3)_3C-O-CH_3 + NaBr$.