Question

If (V) $\xrightarrow[H_2O]{O_3,Zn}$ (R) $\xrightarrow[]{Conc. KOH}$ (S), Identify (S)

Answer 1

Muconic acid (2E,4E–hexadienedioic acid).

Answer 2

Solution Explanation:

1. Identification of V:
   From the overall scheme, V is obtained from n‐hexane over Cr₂O₃–Al₂O₃ at 500°C. In such catalytic reforming reactions, n‐hexane is converted into an aromatic compound. Hence, V is benzene.

2. Ozonolysis of Benzene:
   When benzene is treated with O₃ and then reduced with Zn/H₂O, the aromatic ring is cleaved completely. This gives the intermediate dialdehyde known as muconaldehyde:

   $$\text{Benzene} \xrightarrow{\text{O}_3,\; \text{Zn/H}_2\text{O}} \text{OHC–(CH=CH)}_2–CHO \quad (R)$$

3. Treatment with Conc. KOH:
   The intermediate dialdehyde (R), having non‐enolizable aldehyde groups, undergoes a base–induced Cannizzaro reaction. Both aldehyde groups are converted into carboxylate groups. Acid work–up (if needed) furnishes (2E,4E)‐hexadienedioic acid, commonly known as muconic acid (S).

Thus, (S) is muconic acid.