enter image description here (from Wikipedia)

I am having trouble in the last step where the alkene ozonide is reduced to ketones / aldehydes specifically in the presence of water. My teacher is telling me that water will be abstracting an oxygen atom to form $\ce{H2O2}$.

But why? Both oxygen atoms already have a complete octet, and further are repelled by their electron clouds. Why does water abstract an oxygen atom at all?

  • 4
    $\begingroup$ I was always under the impression that you needed a mild reducing agent, like dimethyl sulfide. I could see the same mechanism working with water, but am rather skeptical, because water is a pretty bad reducing agent, and on top of that if you put H2O2 in there you will get carboxylic acids (that's the "oxidative workup")... $\endgroup$ Commented Aug 6, 2020 at 5:41
  • 1
    $\begingroup$ Agree with orthocresol, a workup with just water makes no sense. It´s probably going to happen if you leave the trioxolane on the shelf with water for a week, and you get a wild mixture of ketones/aldehydes and acids. Not synthetically useful. $\endgroup$
    – Karl
    Commented Aug 6, 2020 at 6:13
  • 1
    $\begingroup$ Not as far as I'm aware. You need to introduce a reducing agent, usually a sulfide, sometimes a phosphine. I think your teacher is in error. $\endgroup$
    – Waylander
    Commented Aug 6, 2020 at 6:42

1 Answer 1


When the ozonide is reduced to Ketone/Aldehyde, We're concerned with what is called the "reductive workup" . We can summarize it like this:

reductive ozonolysis

If we look a little further into the mechanism (of a different alkene): mechanism

Step (e) is what we're concerned with. Water is not having an impact on this reaction in any manner. The main compound here that's assisting this reaction is $\ce{(CH3)_2S}$ which is a mild reducing agent.

Source of the pictures:
Reaction summary
Reaction mechanism

  • 2
    $\begingroup$ I agree. If you work up an ozonolysis reaction mixture with just water, you get the ozonide. DO NOT DO THIS - ozonides are explosive. $\endgroup$
    – Waylander
    Commented Aug 6, 2020 at 8:18
  • $\begingroup$ I'll keep that in mind when I enter the lab (I won't be doing so in the near future :P ) $\endgroup$
    – sai-kartik
    Commented Aug 6, 2020 at 8:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.