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Finding stereoisomers...confused

  1. Jun 10, 2016 #1
    1. The problem statement, all variables and given/known data

    How many distinct stereoisomers exist for the hexadecanoic acid and oleic acid, respectively?
    Please choose from one of the following options.
    • 1, 1
    • 1, 2
    • 2, 2
    • 2, 4

    2. Relevant equations
    None

    3. The attempt at a solution

    If you look at the following images of hexadecanoic (palmitic) acid, and oleic acid, respectively, I cannot find how they arrive at their answer.
    https://upload.wikimedia.org/wikipedia/commons/b/ba/Palmitic_acid.svg

    Oleic-acid-based-on-xtal-1997-2D-skeletal.png

    The correct answer is B.

    In palmitic acid...where is the stereoisomer? I would be looking for something that is either cis/trans or R/S....and none of the sp3 carbons have a stereocenter (they all have at least two H's), and the only double bond is on the carboxylic oxygen. Even if you assume that it is resonant with the hydroxyl group, the CH2 group will freely rotate and not cause any fixation. So I do not see where the stereocenter is..

    In oleic acid, I can see that there is one cis/trans site, but otherwise I have the same issue.

    Why is the carboxylic acid counting as a stereocenter...?
     
  2. jcsd
  3. Jun 11, 2016 #2

    Borek

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    Staff: Mentor

    Must be some error, no stereoisomers here.
     
  4. Jun 11, 2016 #3
    Thanks, that's what I wanted to confirm. Thanks Khan Academy...
     
  5. Jun 11, 2016 #4

    Ygggdrasil

    User Avatar
    Science Advisor

  6. Jun 11, 2016 #5

    Borek

    User Avatar

    Staff: Mentor

    Strange, I was always under impression stereoisomerism is other name for chirality. Seems I was wrong.
     
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