Preparation of Ethers

Symmetrical Ethers

Acid catalyzed dehydration of alcohols.

Diethyl ether is made industrially by this method.  

Williamson Ether Synthesis

The Williamson ether synthesis is a two-step process useful for preparing unsemtrical ethers.  In this process an alcohol is first deprotonated to form an alkoxide intermediate.  The alkoxide intermediate is then treated with an alkyl halide and an ether is formed via an S_N2 reaction.  Because alkoxides are somewhat basic this process is efficient when methyl or primary alkyl halides are utilized.  Secondary and tertiary alkyl halides tend to undergo elimination in the presence of alkoxides.

Stepwise mechanism

Deprotonation (acid/base reaction) of the alcohol with the strong base, sodium hydride, NaH.  This results in the formation of the sodium alkoxide.  Hydrogen gas, H2, is concomitantly formed during this first step.

The ether is formed in the second step via an S_N2 reaction.