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Homework Help: Alkene Diastereomers help?

  1. Oct 15, 2014 #1
    Hey, so I did a lab on alkene Diastereomers ( I saw a similar thread but it wasn't really helpful... However I am guessing the same lab as me).

    We initially had Maleic acid and dissolved it in hot water and mixed it with hydrochloric acid ( carbocation?).The question isn't so clear ( to me anyways). It stats "Will one of the alkene diastereomers [Fumeric and Maleic Acid] be formed preferentially from the carbcation?"

    Wouldn't one of these two be formed anyway after the temporary carbocation is done? I would expect them to have be more stable? ( I might completely wrong with my logic).

    And my experiment shown my unknown ( so the solution we got after the reflux reaction) to be "between" maleic acid and fumeric acid when we analyzed it through thin-layer chromatography. Would that mean that some molecules will be cis-isomers and others trans-isomers?

    p.s sorry for the language; french and haven't done chem in a year ( was in math so im refreshing my memory)

    Thank you for your help
  2. jcsd
  3. Oct 15, 2014 #2


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    Staff: Mentor

    It is about ratio of the products - preferentially means one of the acids will be present in larger amount than the other. If - after reaching equilibrium - concentrations are identical, there is no preference.
  4. Oct 15, 2014 #3
    makes sense so if its half of the way to fumeric acid and maleic acid it would mean both are as stable as the other? However, theoritically, shouldn't fumeric be more stable as it is a trans-isomers? I was thinking this because the carboxyl groups are on the "opposite side" of each other. Sorry for my "dumbed" down logic
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