Preperation of phenol

1) Preparation of Phenols from Haloarenes

Chlorobenzene is an example of haloarenes. We can obtain chlorobenzene by the monosubstitution of a benzene ring. When chlorobenzene fuses with sodium hydroxide at 623K and 320 atm, we obtain sodium phenoxide. Finally, sodium phenoxide on acidification gives phenols.

2) Preparation of Phenols from Benzene Sulphonic Acid

We can obtain Benzenesulphonic from benzene by reacting it with oleum. Benzenesulphonic acid, thus formed, is treated with molten sodium hydroxide at high temperature. This process leads to the formation of sodium phenoxide. Finally, sodium phenoxide on acidification gives phenols.

3) Preparation of Phenols from Diazonium Salts

When we treat an aromatic primary amine with nitrous (NaNO2 + HCl) acid at 273 – 278 K, we can easily obtain diazonium salts. These diazonium salts are highly reactive in nature. Upon warming with water, these diazonium salts finally hydrolyse to phenols. We can also obtain phenols from diazonium salts by treating it with dilute acids.

4) Preparation of Phenols from Cumene

Cumene is an organic compound that we can obtain by the Friedel-Crafts alkylation of benzene with propylene. Upon oxidation of cumene (isopropylbenzene) in presence of air, we obtain cumene hydroperoxide.

Upon further treatment of cumene hydroperoxide with dilute acid, we get the phenols. We also produce acetone as one of the by-products of this reaction in large quantities. Hence, phenols prepared by these methods need purifications.