Primary Phenol Production: The Cumene Process

The dominant industrial method used worldwide for manufacturing phenol is the Cumene process. This process is favoured for its efficiency, cost-effectiveness, and the co-production of acetone, another important chemical.

Cumene Process Explained

The Cumene process involves three main chemical stages:

• Benzene Alkylation: Benzene is reacted with propene (propylene) using an acid catalyst to produce cumene (isopropylbenzene). The balanced chemical equation is:

  $C_6H_6 + CH_3CH=CH_2 \xrightarrow{\text{Catalyst}} C_6H_5CH(CH_3)_2$

• Cumene Oxidation: Cumene is then oxidized with air (oxygen) to form cumene hydroperoxide. This is the key intermediate compound in the process. The reaction is represented as:

  $C_6H_5CH(CH_3)_2 + O_2 \rightarrow C_6H_5C(CH_3)_2OOH$

• Cleavage of Cumene Hydroperoxide: The cumene hydroperoxide is subsequently treated with a dilute acid catalyst (like sulfuric acid), causing it to decompose. This decomposition yields phenol and acetone. This step is also known as the Hock rearrangement. The equation is:

  $C_6H_5C(CH_3)_2OOH \xrightarrow{H^+} C_6H_5OH + (CH_3)_2CO$

Key Intermediate: Cumene Hydroperoxide

As seen in the steps above, cumene hydroperoxide ($C_6H_5C(CH_3)_2OOH$) is the essential intermediate compound. It is synthesized from cumene and then directly converted into both phenol and acetone in the final stage of the process.

Evaluation of Options

Let's look at why the other options are not the primary method or intermediate:

• Dow process: While a historical method for phenol production, it involves the hydrolysis of chlorobenzene, which is less efficient and generates more waste compared to the Cumene process. Toluene is not the primary intermediate here.
• Raschig process: This older method also relies on chlorobenzene and is largely obsolete due to lower yields and harsher conditions. Chlorobenzene is a reactant, not the key intermediate in the same way cumene hydroperoxide is.
• Hock process: This term usually refers to the cleavage step of the Cumene process itself, where cumene hydroperoxide breaks down. Benzene is the starting material, not the intermediate used in the cleavage step.

Therefore, the Cumene process using cumene hydroperoxide as the intermediate is the correct answer for the primary industrial production of phenol.