Alcohols, Phenols and Ethers
10.0 Aryl Ethers
10.0 Aryl Ethers
Phenols are converted to alkyl aryl ethers by reaction in alkaline solution with aryl halide. For the preparation of aryl methyl ethers, dimethyl sulphate ${(C{H_3})_2}S{O_4}$ is frequently used instead of more expensive methyl halide.
The second method is better method to prepare anisole because methyl sulphoates are better leaving group than which causes faster substitutions.
The mechanism of the above reaction can be outlines as follows. In alkaline solution phenol exists as phenoxide ion which acts as nucleophile and attacks the alkyl halide and displaces halide ion
$Ar{O^--} + {\text{ }}C{H_3}---OS{O_2}OC{H_3} \to Ar---O---C{H_3}{\text{ }} + \mathop O\limits^ \odot S{O_2}OC{H_3}$
Since phenoxides are prepared from phenols and since alkyl halide prepared from alcohols. Alkyl aryl ethers are ultimately synthesized from two hydroxyl compounds.
Aryl halides cannot be used in the Williamson's synthesis because o their low reactivity towards the nucleophilic substitution.
