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Homework Help: Ozonolysis of cycloalkene

  1. May 11, 2015 #1

    Suraj M

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    1. The problem statement, all variables and given/known data
    What are the products formed on reductive ozonolysis of 1,4-cyclohexadiene?

    2. Relevant equations

    3. The attempt at a solution
    shouldn't it give propandial?? but the answer says that glyoxal is one of the products, how?
  2. jcsd
  3. May 11, 2015 #2
    yes. do you know its structure?
    Also, propandial is not a product.
  4. May 12, 2015 #3
    What are the reductive work up conditions?
    If you use zinc dust or DMS you will get aldehydes or ketones.
    Use of H2O2 gives you carboxylic acids while sodium borohydride gives you alcohols.
  5. May 12, 2015 #4
    Yes. DMS takes an oxygen atom and gets converted to dimethyl sulphoxide. I think H2O2 gives nascent oxygen which oxidises the products.
    Also, these compounds are also formed as minor products:
    its unstable.
    Also, if methanol is used as a solvent, then one more product will be formed. Try figuring it out.
  6. May 12, 2015 #5
    In the ozonolysis process the methanol is used as a solvent with O3 at -78°C to form ozonide. Using methanol is a necessary condition. We can then use any reagent to get aldehydes, ketones, alcohols or carboxylic acids.

    You might be wanting to say that if methanol is not used then what is the product?
    In that case we will not get ozonide.
  7. May 12, 2015 #6
    I think I used the wrong words. (Typo)? I will check my book and tell you the question later. But what I wanted to say is that, during the reaction, nucleophilic attack of methanol takes place on one of the intermediates To give a different compound.
    [This was given by my chemistry teacher Last month.]
  8. May 12, 2015 #7
    Got it. Actually, this is the question. I was only able to remember some parts before.
    Alcohols react with the carbonyl oxide to give hydroperoxy hemiacetals:
    C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_ozonol10.gif
  9. May 12, 2015 #8

    Suraj M

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    Hi you two, thanks for replying :).
    the thing is, I just got into 12th, just finished, alcohols, phenols.... i didn't understand a lot of what you guys said, my original question was this
    Screenshot (48).png
    I guess all the things you guys were talking about will be taught to me later(wont it? :frown: ) ,
    could you help me solve this question for now? I selected answer D, which was correct because i thought it would give propandial and not glyoxal.. but the question says somethings else..
    PS i hope you did well in your exams Aditya :smile:
  10. May 12, 2015 #9
    D gives 2 moles of a compound other than glyoxal. All others give only glyoxal on ozonolysis. Waite for a few months. Soon you will learn it.
  11. May 12, 2015 #10
    Exams did not go as planned. Atleast I can write jee advanced. The FIITJEE topper here scored 320 in mains.
  12. May 12, 2015 #11
    But the first option benzene gives H2O2 other then glyoxal, so why it is not the answer for question?

    And how come 4th will give glyoxal? To me it is looking propanedial. Is there some rearrangement here that 4th option is giving glyoxal?
  13. May 12, 2015 #12
    Why H2O2? It gives three moles of glyoxal.
    Also, propandial is not a proper name.
  14. May 13, 2015 #13
    Sorry Benzene gives glyoxal as well as ZnO2 in reductive work up.

    Propanedial is a proper name, see
  15. May 13, 2015 #14
    But the question remains unanswered, that are we getting propanedial in 1-4 cyclohexanediene?
  16. May 13, 2015 #15
    yes. 2 moles of propanedial.
  17. May 13, 2015 #16
    And how glyoxal?
  18. May 13, 2015 #17
    question is wrong?
  19. May 13, 2015 #18
    It may be right, some rearrangement can be possible.
    Also benzene is giving glyoxal as well as ZnO2.
    Is there a online calculator to see products?
  20. May 13, 2015 #19
    Why do you think rearrangement is possible?
  21. May 13, 2015 #20
    What can the other reason be and how you can directly say question is wrong?
    Earlier in some posts you were saying that propanedial is not a product.

    In organic chem. there are many rearrangements. Reason could also be because of torsional strain but I am not sure.

    Who can help three of us now?
  22. May 13, 2015 #21
    Thats because I got confused with the structure. I did not get the correct structure using google. @Borek can help us.
  23. May 13, 2015 #22


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    Staff: Mentor

    You need an organiker, not me.
  24. May 13, 2015 #23
    Now, I don't know a decent organiker here in PF.
    Would this problem be solved?:rolleyes:
  25. May 13, 2015 #24

    Suraj M

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    Please Borek, or anyone else, could you help us out.
    I don't understand how glyoxal could be a product from option D,
    even by rearrangement how can you get glyoxal,
  26. May 13, 2015 #25
    Im sure. The question is wrong.
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