JEE Main · 2024 · 29 Jan 2024 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

Let's analyze the reaction sequence step by step:

Step 1: The starting material (benzaldehyde phenylhydrazone) reacts with $\mathrm{NaOH}$ and $\mathrm{I}{}_2$. This is the Hofmann rearrangement or a related reaction. However, given the structure, this appears to be a base-induced elimination or rearrangement.

Step 2: Treatment with $\mathrm{H}{}_3\mathrm{O}{}^{+}$ (acidic hydrolysis).

Step 3: Heating ($\Delta$) causes decarboxylation.

The reaction sequence is:

1. Benzaldehyde phenylhydrazone undergoes oxidation with $\mathrm{I}{}_2/\mathrm{NaOH}$
2. Hydrolysis with $\mathrm{H}{}_3\mathrm{O}{}^{+}$ converts any intermediate to carboxylic acid
3. Heating causes decarboxylation of phenylacetic acid to give ethylbenzene ($\mathrm{C}{}_6\mathrm{H}{}_5-\mathrm{CH}{}_2-\mathrm{CH}{}_3$)

Actually, looking more carefully: the starting material appears to be a hydrazone. The $\mathrm{NaOH}/\mathrm{I}{}_2$ followed by $\mathrm{H}{}_3\mathrm{O}{}^{+}$ and heat would lead to:

• Oxidation and rearrangement
• Formation of carboxylic acid intermediate
• Decarboxylation to give ethylbenzene

Answer: (1) which shows ethylbenzene structure