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Homework Help: Preparation of alkenes from alcohols

  1. Dec 6, 2009 #1
    Q. Draw the structure for all possible alkenes & the alcohols from which they can be prepared.

    CH3-CH=CH-CH2-CH3 <---- CH3-CHOH-CH2-CH2-CH3

    CH2=CH-CH2-CH2-CH3 <---- CH2OH-CH2-CH2-CH2-CH3

    Both in the presence of H+ & heat.

    I also drew Cyclopentanol from which we can prepare Cyclopentene.

    Are these all the possible pentenes? And are these equations correct?

    Thankyou (:
  2. jcsd
  3. Dec 6, 2009 #2


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    I suppose they need to have 5 C atoms , as if not the possibilities would be cosmological :P.
  4. Dec 7, 2009 #3


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    Staff: Mentor

    There is a third pentanol which you have not included.

    There are also branched pentenes - but whether they count may depend on the exact wording of the question.

    Plus zillions of compounds with other number of carbons :wink:

  5. Dec 8, 2009 #4
    Haha Yeaa..I meant pentenes not alkenes :P :$
  6. Dec 8, 2009 #5


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    Good so far, but incomplete. For example you can get to CH2=CH-CH2-CH2-CH3 from two precursor alcohols (and you have written them both) and you can get to CH3-CH=CH-CH2-CH3 from two precursor alcohols, one of which you have shown and one is not shown.

    And of course there are the isomers that Borek mentioned as well.
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