The Williamson Ether Synthesis


The Williamson Ether Synthesis

A long-standing method for the preparation of ethers is the Williamson ether synthesis. Nucleophilic substitution of an alkyl halide by an alkoxide gives the carbon–oxygen bond of an ether:

williamson synthesis

Preparation of ethers by the Williamson ether synthesis is most successful with methyl and primary alkyl halides. 

williamson synthesis

Secondary and tertiary alkyl halides are not suitable, because they react with alkoxide bases by E2 elimination rather than by S N 2 substitution. Whether the alkoxide base is  primary, secondary, or tertiary is much less important than the nature of the alkyl halide. Thus benzyl isopropyl ether is prepared in high yield from benzyl chloride, a primary chloride that is incapable of undergoing elimination, and sodium isopropoxide:

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