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[IMAGE 139]

Total 10 isomers are possible.

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Alkyl aryl ethers are cleaved at the alkyl-oxygen bond due to more stable aryl-oxygen bond. The reaction yields phenol and benzyl halide.

[IMAGE 145]

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[IMAGE 150]

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In [IMAGE 155], the lone pair of oxygen is in conjugation with phenyl group so, it is least basic among the given compounds and is most difficult to protonate.

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Ethers are readily attacked by HI to give an alkyl halide and alcohol. But when heated with excess of HI, the product alcohol first formed reacts further with HI to form the corresponding alkyl iodide.

$\mathrm{R}-\mathrm{O}-\mathrm{R}\text{'}+\underset{\left(\mathrm{excess}\right)}{2\mathrm{HI}}\stackrel{\mathrm{Heat}}{\to }\mathrm{RI}+\mathrm{R}\text{'}\mathrm{I}+{\mathrm{H}}_2\mathrm{O}$

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In case of phenyl methyl ether, methyl phenyl oxonium ion [IMAGE 156] is formed by protonation of ether.  The $\mathrm{O}-{\mathrm{CH}}_3$ bond is weaker than $\mathrm{O}-{\mathrm{C}}_6{\mathrm{H}}_5$ bond as $\mathrm{O}-{\mathrm{C}}_6{\mathrm{H}}_5$ has partial double bond character. Therefore, the attack by ${\mathrm{I}}^{-}$ ion breaks $\mathrm{O}-{\mathrm{CH}}_3$ bond to form ${\mathrm{CH}}_3\mathrm{I}$.

[IMAGE 157]

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Williamson’s ether synthesis reaction involves the treatment of sodium alkoxide with a suitable alkyl halide to form an ether.

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Williamson synthesis is the best method for the preparation of ethers.

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[IMAGE 160]

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[IMAGE 161]