Ozonolysis of alkenes to ketones and aldehydes (reductive workup)
Description: Ozone will cleave carbon-carbon double bonds to give carbonyl compounds such as aldehydes or ketones, after treatment with a reducing agent such as zinc or dimethyl sulfide (“reductive workup”)
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For both ozonolysis mechanisms, the starting material has had at least 1 hydrogen attatched to the alkene carbons, is it possible to do this with 4 alkyl groups?
Oh yes. Absolutely. The C-H bonds where there to show the effect of oxidative vs reductive workup, but ozonolysis works fine for tetrasubstituted alkenes.
What is the purpose of acid here?
Won’t Zinc react with acid to Zinc ion then there is no zinc metal in the system to perform as a catalyst?
The purpose of acid is to protonate the O-O bond, making it easier to reduce. Essentially once the O-O bond is protonated the oxygen is a much better leaving group.
Why must this reaction occur in acid again?
Just the work-up. Breaking the O-O bond makes O- , which is not the greatest leaving group. If acid is around to protonate it to O-OH, then the O-O bond is easier to break.
The conjugate acid is a better leaving group.
What is the preferred acid and is Me2S the aprotic form for this please?