JEE Challenger
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ChemHardAdv 2007 • Paper 2

Intramolecular Aldol Condensation of Hexane-1,6-dial

Cyclohexene on ozonolysis followed by reaction with zinc dust and water gives compound E\mathbf{E}. Compound E\mathbf{E} on further treatment with aqueous KOH\text{KOH} yields compound F\mathbf{F}. Compound F\mathbf{F} is

Options

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

Topics & Concepts

Aldehydes, Ketones and Carboxylic AcidsOzonolysisIntramolecular Aldol CondensationCyclohexene

Step-by-Step Solution

  1. Reductive Ozonolysis:
    Cyclohexene undergoes reductive ozonolysis with O3\text{O}_3 followed by Zn/H2O\text{Zn}/\text{H}_2\text{O} to cleave the double bond, giving hexane-1,6-dial (adipaldehyde):
    Cyclohexene→O3,Zn/H2OOHC−(CH2)4−CHO  (E)\text{Cyclohexene} \xrightarrow{\text{O}_3, \text{Zn}/\text{H}_2\text{O}} \text{OHC}-(\text{CH}_2)_4-\text{CHO}\; (\mathbf{E})

  2. Intramolecular Aldol Condensation:
    Treatment of hexane-1,6-dial with aqueous KOH\text{KOH} initiates an intramolecular aldol condensation. An enolate formed at C-2 attacks the carbonyl carbon C-6, forming a stable 5-membered cyclic β\beta-hydroxyaldehyde. Subsequent dehydration (loss of H2O\text{H}_2\text{O}) yields cyclopent-1-enecarbaldehyde (1-cyclopentenecarboxaldehyde):
    OHC−(CH2)4−CHO→aq. KOH, Δcyclopent-1-enecarbaldehyde  (F)\text{OHC}-(\text{CH}_2)_4-\text{CHO} \xrightarrow{\text{aq. KOH, } \Delta} \text{cyclopent-1-enecarbaldehyde}\; (\mathbf{F})

This matches the structure in Option A.

Correct Answer: A

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