Question

Give the equations of reactions for the preparation of phenol from cumene.

Short answer

Cumene is oxidized to cumene hydroperoxide, then decomposed to phenol and acetone with acid.

Step-by-step solution

Identify the Starting Material

The synthesis of phenol from cumene begins with cumene itself, which is also known as isopropylbenzene. Chemically, cumene is represented as C9H12.

Oxidation to Cumene Hydroperoxide

Cumene is oxidized in the presence of oxygen (O2) to form cumene hydroperoxide. The chemical reaction is as follows: \[ \text{C}_9\text{H}_{12} + \text{O}_2 \rightarrow \text{C}_9\text{H}_{12}\text{O}_2 \] where C9H12O2 is cumene hydroperoxide.

Acid-Catalyzed Decomposition

Cumene hydroperoxide is then subjected to acid-catalyzed decomposition. This step involves the use of an acid catalyst, such as sulfuric acid (H2SO4), leading to the formation of phenol and acetone: \[ \text{C}_9\text{H}_{12}\text{O}_2 \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_5\text{OH} + \text{(CH}_3\text{)}_2\text{CO} \] where C6H5OH is phenol and (CH3)2CO is acetone.

Summary Equation

The net equation for the production of phenol from cumene combines these reactions: \[ \text{C}_9\text{H}_{12} + \text{O}_2 \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_5\text{OH} + \text{(CH}_3\text{)}_2\text{CO} \] This summarizes the complete conversion of cumene to phenol and acetone.

Key concepts

Reactive Oxidation

Reactive oxidation is a critical step in the preparation of phenol from cumene. This process involves converting cumene, a compound known as isopropylbenzene, into cumene hydroperoxide. This conversion is achieved by exposing cumene to oxygen. The general reaction can be represented as follows:

• Cumene (C\(_9\)H\(_{12}\)) reacts with oxygen (O\(_2\)).
• The product formed is cumene hydroperoxide (C\(_9\)H\(_{12}\)O\(_2\)).

Oxidation reactions like this are significant due to their ability to introduce oxygen, leading to more reactive compounds. When cumene is oxidized, the oxygen interacts specifically at the benzylic position of cumene. This interaction is essential in preparing cumene hydroperoxide, which sets the stage for the next step in phenol production.
This process is also a foundation for other oxidative reactions in organic chemistry, where the formation of peroxides plays a crucial role.

Acid-Catalyzed Decomposition

The acid-catalyzed decomposition of cumene hydroperoxide is the next step after reactive oxidation in the preparation of phenol. In this reaction, an acid such as sulfuric acid (H\(_2\)SO\(_4\)) acts as a catalyst to break down cumene hydroperoxide into phenol and acetone. This reaction is represented as:

• Cumene hydroperoxide (C\(_9\)H\(_{12}\)O\(_2\)) is decomposed in the presence of H\(_2\)SO\(_4\).
• The result is phenol (C\(_6\)H\(_5\)OH) and acetone ((CH\(_3\))\(_2\)CO).

In acid-catalyzed reactions, the catalyst speeds up the decomposition without being consumed in the process. Sulfuric acid facilitates the breakdown by providing protons (H\(^+\)), enhancing the electrophilic nature of the reaction site. This decomposition not only produces valuable chemicals like phenol and acetone but also demonstrates a common mechanism used to control and direct organic reactions.

Chemical Reaction Equations

Chemical reaction equations provide a concise way to represent the transformations during the preparation of phenol. They use notation to depict reactants turning into products with the influence of catalysts or specific conditions. For example:

• The initial oxidation of cumene to form cumene hydroperoxide is given by:\[ \text{C}_9\text{H}_{12} + \text{O}_2 \rightarrow \text{C}_9\text{H}_{12}\text{O}_2 \]
• The decomposition reaction of cumene hydroperoxide into phenol and acetone is shown as:\[ \text{C}_9\text{H}_{12}\text{O}_2 \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_5\text{OH} + \text{(CH}_3\text{)}_2\text{CO} \]
• The summary of the overall reaction can be compacted into:\[ \text{C}_9\text{H}_{12} + \text{O}_2 \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_5\text{OH} + \text{(CH}_3\text{)}_2\text{CO} \]

These equations not only summarize the steps but also help visualize the chemical changes occurring. They depict reactants, products, and conditions in a streamlined format, making it easier to understand the overall conversion of cumene into phenol.