By heating alkyl halide with sod. or pot. alkoxides (Williamson synthesis) diethyl ether is formed. This is the most important industrial and laboratory method and may be used for preparing simple as well as mixed ethers. For example :\\\\(C_2H_5ONa+C_2H_5I\\rightarrow C_2H_5O.C_2H_5+NaI\\\\)