PrayogX › Chemistry › Aldehydes, Ketones and Carboxylic Acids

Ozonolysis of natural rubber and the intramolecular aldol that follows

Cleave every C=C of cis-1,4-polyisoprene to reach 4-oxopentanal, confirm it with the iodoform and Tollens tests, then discover why the base-mediated ring closure gives a five-membered ring and, after dehydration, cyclopent-2-en-1-one.

Sub-topics covered

• Reductive ozonolysis of alkenes (O3 then Zn/H2O)
• Structure of natural rubber as cis-1,4-polyisoprene
• Iodoform test for a methyl ketone
• Tollens test for an aldehyde
• Intramolecular aldol and the choice of ring size
• Dehydration to an alpha,beta-unsaturated ketone

What it teaches

• Alkene cleavage and the effect of the work-up
• Enolate formation at the alpha carbon
• Ring strain controls which closure happens
• Conjugation as the thermodynamic driving force

Simulation ID

• ADV-2026-P2-CHE-Q03 · revision 1

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