Preparation of Phenols - Practice Questions & MCQ

Phenol is manufactured from the hydrocarbon, cumene. Cumene (isopropylbenzene) is oxidised in the presence of air to cumene hydroperoxide. It is converted to phenol and acetone by treating it with dilute acid. Acetone, a by-product of this reaction, is also obtained in large quantities by this method. The reaction occurs as follows:

From Haloarenes
Chlorobenzene is fused with NaOH at 623K and 320 atmospheric pressure. Phenol is obtained by acidification of sodium phenoxide so produced. The reaction occurs as follows.

From Benzenesulphonic acid
Benzene is sulphonated with oleum and benzene sulphonic acid so formed is converted to sodium phenoxide on heating with molten sodium hydroxide. Acidification of the sodium salt gives phenol. The reaction occurs as follows:

From Diazonium salts
A diazonium salt is formed by treating an aromatic primary amine with nitrous acid (NaNO₂ + HCl) at 273-278 K. Diazonium salts are hydrolysed to phenols by warming with water or by treating with dilute acids. The reaction occurs as follows.