Ozonolysis
Key Questions
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An ozonide is the 1,2,4-trioxolane structure that is formed when ozone reacts with an alkene,
The first intermediate in the reaction is called a molozonide.
A molozonide is a 1,2,3-trioxolane (tri ="three"; oxa = "oxygen"; olane = "saturated 5-membered ring").
The molozonide is unstable. It rapidly converts in a series of steps to an ozonide.
An ozonide is a 1,2,4-trioxolane. It rapidly decomposes in water to form carbonyl compounds such as aldehydes and ketones.
The video below shows the formation of the molozonide and ozonide intermediates as part of the mechanism.
Ernest Z.
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1
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Feb 15 2015
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Ozonolysis does not tell you about any stereochemistry there may have been in the original alkene.
Reductive ozonolysis converts an alkene into a pair of carbonyl compounds.
If the R groups are different, we can have cis/trans or E/Z stereochemistry.
If R₂ and R₄ are the groups with higher priority, 1 is a Z alkene. 2 is an E alkene.
But both give the same ozonolysis products.
You cannot distinguish between cis-but-2-ene and trans-but-2-ene by reductive ozonolysis.
They both give acetaldehyde as the only ozonolysis product.
Ernest Z.
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2
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Dec 28 2014