Ozonolysis
Ozone adds to an alkene to form an ozonide, which is cleaved by zinc and water to give aldehydes or ketones.
But-2-eneCH₃CH=CHCH₃Alkene - Step 1
(i) O₃ (ii) Zn, H₂O
EthanalCH₃CHOAldehyde
How it works
- Ozone adds across the C=C to give a molozonide, then an ozonide.
- Zn and water cleave the ozonide.
- Two carbonyl compounds form, and zinc prevents over-oxidation to acids.
What it makes
Aldehydes and ketones; also locates a double bond.
Where it fails
Zinc is needed to keep aldehydes from being oxidised by hydrogen peroxide.
Class 11, Chapter 9 Hydrocarbons
Ozonolysis: quick answers
What is the role of zinc dust?
It reacts with H2O2 formed, so aldehydes are not oxidised to acids.
What does but-2-ene give?
Two molecules of ethanal.
What does propene give?
Ethanal and methanal.