Preparation of Ethers, Epoxides, and Thioethers:
Ethers
The Williamson ether synthesis is the best technique of preparing ethers as shown in figure. The procedure includes the SN2 reaction among a metal alkoxide and a primary alkyl halide or tosylate. The alkoxide needed for the reaction is prepared via treating an alcohol with a strong base like sodium hydride. Another procedure is to treat the alcohol directly with the alkyl halide in the existence of silver oxide, thus avoiding the require to prepare the alkoxides beforehand.
Figure: Synthesis of ethers.
If unsymmetrical ether is being synthesized, the most hindered alkoxide should be reacted along with the very simple alkyl halide, rather than another way round. As this is an SN2 reaction, primary alkyl halides react better than as compared to secondary or tertiary alkyl halides.
Figure: Choice of synthetic routes to an unsymmetrical ether.