Williamson ether synthesis
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Williamson ether synthesis was developed by Alexander Williamson in 1850. It involves the reaction of an alkoxide ion with primary alkyl halides and tosylates via an SN2 reaction.
The Williamson reaction is a nucleophilic substitution in which the alkoxide ion displaces the halide, forming an ether and an inorganic salt. An example is the reaction of sodium ethoxide with chloroethane to form diethyl ether and sodium chloride:
- Na+C2H5O− + C2H5Cl → C2H5OC2H5 + Na+Cl−
This reaction is of importance in the history of organic chemistry as it is by this reaction that the structure of ethers was proved.
Typical substrates are primary and secondary alkyl halides, dialkyl sulfates, and alkyl sulfonates.
Williamson ether synthesis is important because of its versatility; it can be used to make unsymmetrical ethers as well as symmetrical ethers.
If we wish to prepare an unsymmetrical dialkyl ether, we have a choice of two combinations of reagents; one of these is nearly always better than the other.
