The reaction between a primary haloalkane and an alkoxide (or alcohol in a basic medium) is the most important method for preparing ethers. This reaction is known as the Williamson synthesis.

 
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This reaction proceeds through the S N 2 mechanism.
 
The strong basicity of alkoxides leads to elimination reactions with secondary and tertiary substrates, forming alkenes instead of ethers.
 
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Another situation in which Williamson does not yield ethers is in the case of using hindered alkoxides, such as potassium tert Due to its large size tert -butoxide eliminates even with primary substrates.
 
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With primary haloalkanes and especially with haloalkanes that lack b , Williamson's performance is very good.
 
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