Oxidative cleavage of alkenes to give ketones/carboxylic acids using ozone (O3) – (“oxidative workup”)
Description: Ozone will cleave carbon-carbon double bonds to give ketones/carboxylic acids after oxidative workup.
[private_ReactionGuide]
Notes: The initial product of this reaction is an ozonide. Treatment of the ozonide with acid and an oxidant such as hydrogen peroxide (H2O2) will convert any aldehydes to carboxylic acids. Note that any C–H bonds on the alkenes are converted to C–OH bonds, giving carboxylic acids.
Examples:
Notes: Note how every C–H bond on the alkene is converted into a C–OH bond to give a carboxylic acid. Also note that example 3 shows cleavage of a cyclic alkene to give a linear compound. In example 4, cleavage of a terminal alkene results in CO2.
Mechanism: The first step of the reaction is a cycloaddition of ozone with the alkene (Step 1, arrows A, B, and C). The second step is a reverse cycloaddition, resulting in cleavage of the carbon-carbon single bond (Step 2, arrows D, E, and F). The oxygen of the carbonyl oxide then performs a 1,2-addition on the other carbonyl (Step 3, arrows G and H) giving a negatively charged oxygen that performs a 1,2-addition on the carbonyl carbon of the carbonyl oxide to give the ozonide (Step 4, arrows I and J).
With warming, the ozonide breaks down to the aldehyde and a carbonyl oxide (Step 5, arrows K, L, and M). Addition of peroxide to the aldehyde then occurs (Step 6, arrows N and O). This is followed by proton transfer (Step 7, arrows P and Q) and then removal of a proton with base to give the carbonyl (C=O) (Step 8, arrows R, S, and T).
Notes: There are other reasonable ways to draw this mechanism, particularly other ways of drawing proton transfer in Step 7 and other species that could act as bases in Step 8.
[/private_ReactionGuide]
{ 10 comments… read them below or add one }
For example 3, is there a way to go back to the original 1-methyl-1-cyclohexene??
I can’t seem to get the cyclic structure back…
I’m not sure what you mean by “go back” to the original. If you mean, understand how the product came from the starting material, I’d suggest numbering all the carbons and going from there.
Oh! I mean is there a reagent/mechanism that can revert the 6-oxoheptanoic acid back to the methylcyclohexene?
The closest mechanism I got to was:
1. reduce the 6-oxoheptanoic acid with LAH
2. protect the alcohol that formed where the carboxylic acid was with dihydropyran
3. oxidize the ketone-turned alcohol back in a ketone
4. treat with acid to retrieve the carboxylic-formed alcohol…. but from here, I get an ester if i use the carboxylic-formed alcohol to attack the ketone..
Nice article! Thanks.
Is it be possible to cleave the alkene only by hydrogen peroxide, as ozone have safety problems commercially.
No, never. You need a strong oxidant like KMnO4 or O3.
Is it possible to react organic peroxides with alkenes to get carbonyl groups? Only H2O and O2 would be present. What about primary alcohols?
By themselves, peroxides will not lead to cleavage of alkenes. Peroxides can lead to oxidation of aldehydes to carboxylic acids, but by themselves, will not oxidize alcohols to aldehydes. There are metal-based catalysts capable of doing both transformations with peroxide as a reoxidant, however.
Thanks James. What about cobalt and other transition metals? Is there a good resource to read more about the reactions of water/oxygen/peroxides/carbonyls with alcohols/olefins? Thanks in advance.
The very last image doesn’t seem to be working for me!
fixed. Thanks!