Identify the substrate ' X ' in the following reaction.
$\text{X} + \underset{(\text{air})}{\text{O}_2} \xrightarrow[\text{ii) dil HCl } \Delta]{\text{i) Co-naphenate } 423 \text{ K}} \text{Phenol} + \text{Acetone}$
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Whenever you see "Phenol + Acetone" as products, the starting material is always Cumene (Isopropyl benzene).
Step 1: Understanding the Concept:
The given reaction scheme depicts the major commercial method for the large-scale preparation of phenol and acetone. This specific industrial process is universally known as the Cumene process. Step 2: Key Formula or Approach:
Approach: Recognize the final products (phenol and acetone) and the specific oxidizing conditions to identify the starting material of the Cumene process. Step 3: Detailed Explanation:
In the Cumene process, the starting substrate 'X' is cumene. The systematic IUPAC name for cumene is isopropyl benzene.
The reaction proceeds in two fundamental steps:
1. Oxidation Step: Isopropyl benzene (cumene) undergoes aerial oxidation in the presence of a catalyst like cobalt naphthenate at $423 \text{ K}$ to form cumene hydroperoxide.
\[ \text{C}_6\text{H}_5\text{CH(CH}_3)_2 + \text{O}_2 \longrightarrow \text{C}_6\text{H}_5\text{C(OOH)(CH}_3)_2 \]
2. Acid Hydrolysis Step: The intermediate cumene hydroperoxide is then treated with dilute acid (such as $\text{HCl}$ or $\text{H}_2\text{SO}_4$) and heated. It undergoes a rearrangement and cleavage to yield phenol and acetone.
\[ \text{C}_6\text{H}_5\text{C(OOH)(CH}_3)_2 \xrightarrow{\text{H}^+, \Delta} \text{C}_6\text{H}_5\text{OH} + \text{CH}_3\text{COCH}_3 \]
This synthetic method is highly favored industrially because it simultaneously yields two highly valuable chemical products from a relatively cheap starting material. Step 4: Final Answer:
The starting substrate X is isopropyl benzene.