Editing Ether (section)

===Williamson and Ullmann ether syntheses===
[[Nucleophilic displacement]] of [[alkyl halide]]s by [[alkoxide]]s
: R–ONa + R′–X → R–O–R′ + Na[[Halide|X]]
This reaction, the [[Williamson ether synthesis]], involves treatment of a parent [[Alcohol (chemistry)|alcohol]] with a strong [[Base (chemistry)|base]] to form the alkoxide, followed by addition of an appropriate [[aliphatic compound]] bearing a suitable [[leaving group]] (R–X). Although popular in textbooks, the method is usually impractical on scale because it cogenerates significant waste.

Suitable leaving groups (X) include [[iodide]], [[bromide]], or [[sulfonate]]s. This method usually does not work well for aryl halides (e.g. [[bromobenzene]], see Ullmann condensation below). Likewise, this method only gives the best yields for primary halides. Secondary and tertiary halides are prone to undergo E2 elimination on exposure to the basic alkoxide anion used in the reaction due to steric hindrance from the large alkyl groups.

In a related reaction, alkyl halides undergo nucleophilic displacement by [[phenoxide]]s. The R–X cannot be used to react with the alcohol. However [[phenols]] can be used to replace the alcohol while maintaining the alkyl halide. Since phenols are acidic, they readily react with a strong [[Base (chemistry)|base]] like [[sodium hydroxide]] to form phenoxide ions. The phenoxide ion will then substitute the –X group in the alkyl halide, forming an ether with an aryl group attached to it in a reaction with an [[SN2|S<sub>N</sub>2]] mechanism.

: C<sub>6</sub>H<sub>5</sub>OH + OH<sup>−</sup> → C<sub>6</sub>H<sub>5</sub>–O<sup>−</sup> + H<sub>2</sub>O
: C<sub>6</sub>H<sub>5</sub>–O<sup>−</sup> + R–X → C<sub>6</sub>H<sub>5</sub>OR

The [[Ullmann condensation]] is similar to the Williamson method except that the substrate is an aryl halide. Such reactions generally require a catalyst, such as copper.<ref>{{cite journal |last1=Frlan |first1=Rok |last2=Kikelj |first2=Danijel |title=Recent Progress in Diaryl Ether Synthesis |journal=Synthesis |date=29 June 2006 |volume=2006 |issue=14 |pages=2271–2285 |doi=10.1055/s-2006-942440}}</ref>