Hydroxylation with Osmium Tetraoxide

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The discussion revolves around the confusion regarding the stereochemistry of diol formation when 1-methylcyclohexene is treated with osmium tetroxide (OsO4) and hydrogen peroxide (H2O2). Participants clarify that OsO4 typically leads to syn addition, forming an osmate ester that should yield a syn diol, raising questions about the reported anti addition in the problem. The possibility of a free radical mechanism initiated by H2O2 is considered, but participants note that H2O2 likely regenerates OsO4, maintaining the syn pathway. The conversation highlights the lack of organic chemistry expertise in the forum and suggests seeking help from other platforms or mentors. Ultimately, there is a consensus that the textbook may contain an error regarding the expected product.
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Homework Statement


I know that alkenes when treated with OsO4 in pyridine undergo syn 1,2-dihydroxylation. This forms an osmate ester which when treated with NaHSO3 in water gives a diol by syn addition.
However, in one of the problems, 1-methylcyclohexene treated with OsO4 and then H2O2 gave a diol by anti addition.
The attempt at a solution
I think that it won't add by anti fashion in the first place. Even if it is possible, would it be by some free radical mechanism?
Please explain.
 
Hey! Hasn't anybody seen this...
@Borek @TeethWhitener @Ygggdrasil Come on say something...Anything
I suscpect that this question is wrong but I need clarification. It's useless bumping it again, it might backfire.
I know I'm being a cranky kid but still...please
 
Sorry, organic chemistry is something I don't touch even with a long stick.
 
You got the ozonolysis question...
Never mind
 
I also can't figure out why the product would be anti. If this is part of a class, perhaps ask your professor or a teaching assistant.
 
Ygggdrasil said:
I also can't figure out why the product would be anti. If this is part of a class, perhaps ask your professor or a teaching assistant.
Unfortunately, my professor isn't doubt friendly. Plus, the book I'm referring to is wayyy out of our syllabus (but I know the theory well), so she wouldn't even look at it. I tried...
 
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Can you ask any other Mentor or Organic Chemistry expert you know to take a look at this?
I know @TeethWhitener & @DrClaude can look at this, but both of them are inactive for a while now...
(P.S. Sorry I have to resort to such means...wandering like a door-to-door salesman...but the discussion hasn't triggered even after a week...)
 
OsO4 can be rendered catalytic with judicious use of a sacrificial oxidant like H2O2. I doubt this affects stereospecificity.
 
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  • #10
Physics Fourms may lack the organic chemistry expertise to answer your question. Perhaps try www.chemicalforums.com or reddit.com/r/chemistry
 
  • #11
Ygggdrasil said:
Physics Fourms may lack the organic chemistry expertise to answer your question. Perhaps try www.chemicalforums.com or reddit.com/r/chemistry
I'll give it a shot.
It's not that we lack the expertise, it's just that we're relying too much on @TeethWhitener (no offence to you). He's the only one I know who helps regularly with organic chemistry homework.
If there were more experts, even his job would've been easier. I'm not saying he's unreliable...but you know, more experts-more inputs-better inputs is the way it works.
 
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  • #12
I know even @DrClaude can look at this, but he's gone cold for over a month. Oh wait, I just remembered that even @mjc123 and @SammyS can look at this. Maybe, they can figure it out.
 
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  • #13
Coincidentally, OsO4 is so expensive that you can't even perform this reaction in a lab to check the outcome.
Plus, 1-methylcyclohexene is probably not even isolable, so we'd have to generate it in situ in some other reaction. So even if everything else is available, it's too much of a fuss.
 
  • #14
If you think about the mechanism of this, the osmate ester intermediate must give a syn diol. An anti outcome has to mean that a free radical mechanism is initiated by the H2O2 (as in our usual HBr anti Markovnikov addition). But howwww?
 
  • #15
baldbrain said:
If you think about the mechanism of this, the osmate ester intermediate must give a syn diol. An anti outcome has to mean that a free radical mechanism is initiated by the H2O2 (as in our usual HBr anti Markovnikov addition). But howwww?
In my experience, H2O2 simply regenerates OsO4 from OsO2(OH)2 (hence the catalytic activity), so the syn intermediate isn't changed.
 
  • #16
baldbrain said:
OsO4 is so expensive
It's not that expensive, especially if you use it as part of a catalytic system.
baldbrain said:
I'm not saying he's unreliable
I was on vacation for a week.
 
  • #17
TeethWhitener said:
I was on vacation for a week.
No dude, don't get pissed. I said that not because you were inactive but because you're the only one I know who actively engages in organic chemistry questions.
Take this question's case itself as an example. We started bombarding you as soon as you were back from your vacation.
So if there are more active expects, we don't need to rely on you. As I said,
baldbrain said:
more experts-more inputs-better inputs
 
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  • #18
TeethWhitener said:
In my experience, H2O2 simply regenerates OsO4 from OsO2(OH)2 (hence the catalytic activity), so the syn intermediate isn't changed.
I even watched the Khan Academy video, and they seem quite alright with the syn product even with H2O2. So probably, there's a misprint in my book. A huge one that could've cost me.
 
  • #19
Thank you @Borek & @Ygggdrasil for helping me as much as you could. I know that mentioning someone in a message to draw their attention is unethical. I'll avoid doing it again.
And @TeethWhitener , if you're pissed, I'm sorry.
 

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