Alcohols, Phenols and Ethers: Methods of Preparation: Laboratory Synthesis of Phenols (For CBSE, ICSE, IAS, NET, NRA 2022)

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Methods of Preparation

Laboratory Synthesis of Phenols

From Arene Diazonium Salts

  • It is the most general method of preparation of phenols and requires mild conditions.
  • Arene diazonium salts or aromatic diazonium salts are obtained by the diazotization of primary aromatic amines as given below:
From Arene Diazonium Salts

The arene diazonium salt on hydrolysis yields phenol

From Arene Diazonium Salts

Alkali Fusion of Sodium Benzene Sulphate

  • This was the first commercial synthesis of phenol developed in Germany in 1890.
  • Sodium benzene sulphate is fused with sodium hydroxide to give sodium phenoxide which on acidification yields phenol.
Alkali Fusion of Sodium Benzene Sulphate

Industrial Synthesis of Phenols

Dow Process

In this process, chlorobenzene is heated with aqueous sodium hydroxide under pressure. Sodium phenoxide so produced on acidification gives phenol.

Dow Process

From Cumene Hydroperoxide

The reaction between benzene and propene in presence of phosphoric acid yields cumene.

From Cumene Hydroperoxide

Cumene is then oxidized to cumene hydroperoxide by air.

From Cumene Hydroperoxide

In the final step, cumene hydroperoxide is treated with sulphuric acid to give phenol and acetone on hydrolytic rearrangement.

From Cumene Hydroperoxide

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