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ozonolysis reaction

Discussion in 'DAT Discussions' started by Awuah29, Apr 21, 2007.

  1. Awuah29

    Awuah29 Christian predent 7+ Year Member

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    Oct 13, 2003
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    When alkene react with O3 you have either aldehyde or ketone forming. When do you determine which product will form? Or do both form at the same time?
     
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  3. Lonely Sol

    Lonely Sol cowgoesmoo fan! 10+ Year Member

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    Well, Carboxylic acid can form too. Here is the difference:

    For aldehyde to form: Must be a terminal alkene and must have Zn/cl as the reagent in order to stop the further oxidation to carboxylic acid.

    For Keytone to form: Must be a secondary alkene.

    For carboxylic acid to form: Must be a terminal alkene, that is missing the zn/cl reagant. Do the aldehyde formed gets further oxidized by air to carboxylic acid.
     
  4. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    Actually...ozone/Zn/water reacted with an alkene will always give the product of the form HCOH, RCOH, RCOR'...no carboxy acid with ozone

    However, ozone/hydrogen peroxide will give carboxy acid if a hydrogen is present on the carbon. ethylene gives 2 HCOOH...RC=CH2 gives RCOOH and HCOOH...see the pattern?

    Then comes Alkene reacted hot potassium permanganate. If two H's are present on the carbon we get full blown oxidation
    Ethylene reacted with hot KMnO4 gives two Carbon dioxide

    If R-CH=CH-R then we just get two R-COOH

    Most of the practice questions I've seen (and I have seen A LOT of Ochem practice questions) don't really expose understanding of the last two reactions.....but ozone/Zn/water is a must
     
  5. Lonely Sol

    Lonely Sol cowgoesmoo fan! 10+ Year Member

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    Yea, but since our atmosphere is the best oxidizing agent, would it just oxid the RCHO to RCOOH, if not Zn/H30 present?! (I always thought it would, but i might be wrong)
     
  6. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    True...BUT for DAT purposes go with the immediate product...check any practice question...destroyer achiever etc

    Yes...aldehydes oxidize very easily in the presence of oxygen...the same goes for ethanol...wine + air = acetic acid
     
  7. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    Immediate....further oxidations take time to develop....but a lot of the choices will have a carboxy acid...stay away
     
  8. Lonely Sol

    Lonely Sol cowgoesmoo fan! 10+ Year Member

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    Thanks, I guess thats what happens when you get too technical! Would they have ambigous ques. like that on real DAT?!
     
  9. Greensalad

    Greensalad 10+ Year Member

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    Apr 16, 2007
    Where did you find this? I can't find it anywhere.
     
  10. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    Did you try looking in your ochem textbook? If I recall correctly...I think the McMurry book has that reaction....most textbooks should have that reaction.

    Here is an immediate source I was able to find online

    http://www.cem.msu.edu/~reusch/VirtualText/addene2.htm

    Keep scrolling and you'll find it
     
  11. skyisblue

    skyisblue 2+ Year Member

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    Dec 25, 2006
    For ozonolysis of an alkene, it depends on how many substituents there are on the double bond.

    We know that ozonolysis/reduction cleaves the double bond and carbonyl functional group forms...

    If it's tetra substituted, then you get 2 ketones when the molecule splits.

    If it's tri substituted, then you get a ketone and an aldehyde.

    If it's di substituted, then you get 2 aldehydes.....etc. etc....

    Draw it out, then everything will make sense to you.
     
  12. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    The variations with hot KMnO4 and hydrogen peroxide are worth noting....just to have something up your sleave with respect to the DAT's bag of tricks
     
  13. skyisblue

    skyisblue 2+ Year Member

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    Dec 25, 2006
    That would be so tricky if the DAT had something like that.
     
  14. Awuah29

    Awuah29 Christian predent 7+ Year Member

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    Oct 13, 2003
    New Jersey
    do you have a links that I can visualize it
    thanks
     
  15. skyisblue

    skyisblue 2+ Year Member

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    Dec 25, 2006
    I don't have links to this, but just draw it out. You'll see a pattern, and this will no longer be a mystery for you.
     
  16. Greensalad

    Greensalad 10+ Year Member

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    Apr 16, 2007
    I can't find that in my book. Mind explaining it please?
     
  17. Greensalad

    Greensalad 10+ Year Member

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    Apr 16, 2007
    I have that book, but I can't find the hydrogen peroxide reaction under ozone.
     
  18. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    You're right...I just checked the book...instead they have a variation with KMnO4 w/ H+ (not acetic acid)....

    I would just take the time to memorize hot KMnO4....usually when you see an oxidizing agent in harsh conditions...it should send a red flag for full blown oxidation...thus if alkene is terminal think +4 oxidation = carbon dioxide

    But....don't confuse hot KMnO4 w/ cold KMnO4

    Check out that link....all variations are there!!!

    This link is good too, if you need to put yourself through an ochem boot camp!!!

    http://www.chemistry.ohio-state.edu/organic/flashcards/
     
  19. poc91nc

    poc91nc Banned Banned 7+ Year Member

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    Nov 5, 2006
    Whoops...I originally posted that link for the variation w/ ozone and hydrogen peroxide. Sorry!!!

    I remember now...I saw that variation of hot KMnO4 in a book called How to Succeed in Organic Chemistry. All alkene oxidations were layed out very nicely in that book. Unfortunately that book is out of print.

    If you're are that bent on finding an explanation for that reaction...go to your undergraduate library...I am sure you can find a textbook with that reaction
     

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