The Williamson ether synthesis is a nucleophilic substitution reaction that leads to the formation of an ether by reacting an alkyl halide with an alkoxide ion:

The reaction can also be used to prepare an ether from two alcohol starting materials by first converting the OH moiety on one of the alcohols to a better leaving group such as tosylate, nosylate, brosylate, trifluoromethanesulfonate, or other sulfonate.

The reaction works best with primary alkyl halides and alcohols. Tertiary alkyl halides will not undergo an S_N2 displacement. Depending on the alkoxide, either elimination products (by either an E1 or E2 mechanism) or S_N1 products generally will be observed.

Mechanism:

The reaction proceeds primarily through an S_N2 (second order nucleophilic substitution) mechanism, particularly when a primary alkyl halide is used. The reaction can also proceed through an S_N1 (first order nucleophilic substitution) mechanism. E1 and E2 elimination products can also be observed when secondary alkyl halides are used.

The reaction rate for alkyl chlorides and bromides can be improved by adding a catalytic amount of sodium iodide to the reaction in a variation known as the Finkelstein reaction. The highly nucleophilic iodide ion displaces chloride or bromide to form an alkyl iodide intermediate which then reacts with the alkoxide.

Experimental Procedure:

See 3-(2-methoxyethoxy)prop-1-ene for an example of the laboratory procedure.

Tags: chemistry, ether, name reaction, Name Reactions, organic chemistry, Sn2, synthesis

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