JEE Challenger
More from Organic Chemistry - Basic Principles

Identify Products V and W in Organic Reaction Sequence

For the provided sequence of chemical reactions, determine the identity of products VV and WW respectively:

Question Diagram 1

Options

A
Option A Diagram 1
Correct
B
Option B Diagram 1
C
Option C Diagram 1
D
Option D Diagram 1

Step-by-Step Solution

To determine the identity of products VV and WW in the given reaction sequence, let us analyze each chemical transformation step-by-step:

Step 1: Formation of Product VV

Compound QQ (maleic anhydride) contains a carbon-carbon double bond between two carbonyl carbons. Maleic Anhydride (Q)→ΔH2/NiSuccinic Anhydride (V)\text{Maleic Anhydride } (Q) \xrightarrow[\Delta]{\text{H}_2 / \text{Ni}} \text{Succinic Anhydride } (V) Catalytic hydrogenation (H2/Ni,Δ\text{H}_2/\text{Ni}, \Delta) selectively reduces the alkene double bond (−CH=CH−-\text{CH}=\text{CH}-) to an alkane single bond (−CH2−CH2−-\text{CH}_2-\text{CH}_2-) without affecting the cyclic anhydride group. Therefore, product VV is succinic anhydride.


Step 2: Intermolecular Friedel-Crafts Acylation

When benzene reacts with succinic anhydride (VV) in the presence of anhydrous AlCl3\text{AlCl}_3, an intermolecular Friedel-Crafts acylation reaction occurs: Benzene+Succinic Anhydride (V)→AlCl3 (anhydrous)4-oxo-4-phenylbutanoic acid\text{Benzene} + \text{Succinic Anhydride } (V) \xrightarrow{\text{AlCl}_3 \text{ (anhydrous)}} \text{4-oxo-4-phenylbutanoic acid} C6H6+C4H4O3→AlCl3C6H5−C(=O)−CH2−CH2−COOH\text{C}_6\text{H}_6 + \text{C}_4\text{H}_4\text{O}_3 \xrightarrow{\text{AlCl}_3} \text{C}_6\text{H}_5-\text{C}(=\text{O})-\text{CH}_2-\text{CH}_2-\text{COOH}


Step 3: Clemmensen Reduction

The intermediate 4-oxo-4-phenylbutanoic acid undergoes a Clemmensen reduction using Zn-Hg/HCl\text{Zn-Hg/HCl}: C6H5−C(=O)−CH2−CH2−COOH→Zn-Hg/HClC6H5−CH2−CH2−CH2−COOH\text{C}_6\text{H}_5-\text{C}(=\text{O})-\text{CH}_2-\text{CH}_2-\text{COOH} \xrightarrow{\text{Zn-Hg/HCl}} \text{C}_6\text{H}_5-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{COOH} The aromatic ketone (C=O\text{C=O}) group is reduced completely to a methylene (-CH2-\text{-CH}_2\text{-}) group, forming 4-phenylbutanoic acid.


Step 4: Intramolecular Friedel-Crafts Acylation to Form WW

Heating 4-phenylbutanoic acid with phosphoric acid (H3PO4\text{H}_3\text{PO}_4) acts as a dehydrating acid catalyst, driving an intramolecular cyclization (Friedel-Crafts acylation): C6H5−CH2−CH2−CH2−COOH→H3PO41-tetralone (W)+H2O\text{C}_6\text{H}_5-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{COOH} \xrightarrow{\text{H}_3\text{PO}_4} \text{1-tetralone } (W) + \text{H}_2\text{O} This forms a fused six-membered ring containing a carbonyl group, known as 1-tetralone (α\alpha-tetralone).


Conclusion:

  • Product VV: Succinic anhydride
  • Product WW: 1-tetralone (α\alpha-tetralone)

This sequence corresponds to Option A.