Question

In the preparation of a methyl phenyl ether from phenol and methyl iodide the crude product may contain unreacted phenol. how would you remove this?

Answer 1

Well give it a wash with aqueous sodium hydroxide....

Explanation:

You gots `H_3C-O-C_6H_5`, and `HO-C_6H_5`, and `H_3C-I` in a mix....

Certainly a good wash with sodium hydroxide, which will react with the ACIDIC phenol to give phenoxide....

`C_6H_5OH(aq) + NaOH(aq) rarr C_5H_5O^(-)Na^+ + H_2O(l)`

...will partition the phenoxide to the AQUEOUS milieu. The ether will be confined to the ORGANIC phase....

Of course, any unreacted methyl iodide will also be confined to the organic phase, however, the methyl iodide is a whole lot more volatile than phenol or the phenolic ethers....

And to get to your phenol, acidify the aqueous phase, so as to reprotonate the phenoxide to give phenol,

`PhO^(-)""^(+)Na + HCl(aq) rarr PhOH(aq) + NaCl(aq)`

and then extract this organic solute with several volumes of ether, and strip off the ether to give crude phenol.....