This reaction is general methods of preparation from alkyl halides

According to this question the reaction which is used for the synthesis of ether is undergoes in ${\mathrm{S}}_{{\mathrm{N}}_2}$ reaction

It is formed from the reaction of alkyl halides and sodium ethoxide

$\mathrm{R}-\mathrm{X} + {\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{O}}^{-} {\mathrm{Na}}^{+} \stackrel{\mathrm{ester}}{\to } \mathrm{R} -\mathrm{O}-{\mathrm{C}}_2{\mathrm{H}}_5$