Phenolic ethers (alkaryl ethers, `ArOR`) are prepared by

Options

A. heating sodium phenoxide with alkyl halide in ethanol solution
B. treating an alkaline solution of a phenol with alkyl sulphate
C. Both `(1) and `(2)`
D. heating sodium alkoxide with aryl halide in ethanol solution

Answer

C

Explanation

Phenols are converted into alkyl aryl ethers by reaction in alkaline solution with alkyl halides. For the preparation of aryl methyl ethers, methyl sulphate, `(CH_(3))_(2)SO_(4)`, is frequently used instead of the more expensive methyl halides.
In alkaline solution a phenol exsts as the phenoxide ion which (acting as a nucleophilic reagent) attacks the halide (or the sulphate) and displaces halide ion (or sulphate ion).

This is familiar williamson synthesis. it is more conveniently carried out here than when applied to the preparation of dialkyl ethers, where the sodium alkoxides must be prepared by direct action of `Na` metal on dry alcohols.
Notice that methyl sulphate is a good methylating agent in the williamson synthesis because the anions, `CH_(3)OSO_(3)^(-)` and `SO_(4)^(2-)`, are very weakly basic and hence are very good leaving groups. sulphonic acid esters, such as the tosylates, can also serve in place of alkyl halides in the williamson synthesis. two important phenolic ethers anisole `(C_(6)H_(5)OCH_(3) bp155^(@)C)` and phenetole `(C_(6)H_(5)OC_(2)H_(5),bp 172^(@)C)` are prepared industrially by the alkylation of phenol with methyl or ethyl sulphates or with methyl and ethyl esters of `p-`toluene sulphonic acid.
4. Because of their low reactivity toward nucleophilic substitutio, aryl halides cannot (in general) be used in the williamson synthesis. for example, for the preparation of an alkyl aryl ether we can consider two combination of reactants, but one combination can usually be rejected out of hand.
since phenoxides are prepared from phenols and since alkyl halides are conveniently prepared from alcohols, synthesized from two hydroxy compounds.