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Stereoisomerism problem

  1. May 21, 2006 #1
    How many stereocenter containing isomers of c5h10 are there where the molecule must contain one ring?

    I identified the cis and trans forms of 1,2-dimethylcyclopropane, but I think my TA said there was one more form containing a cyclopropane ring.... but I can't remember for sure. Is C1 on 1,1-dimethylcyclopropane a stereocenter? It doesn't seem to have four different substituents.

    So confusing.
  2. jcsd
  3. May 21, 2006 #2


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    You're right that the C1 on 1,1-dimethylcyclopropane doesn't have four different substituents.

    I can't seem to think of any other C5H10 cyclic molecules that would have a stereocenter.

    The isomers of C5H10 with rings I can think of would be cyclopentane, methylcyclobutane, 1,1-dimethylcyclopropane, 1,2-dimethylcyclopropane, and ethylcyclopropane. The only ones with stereocenters are the isomers of 1,2-dimethylcyclopropane as you mentioned.
  4. May 21, 2006 #3
    Hey, I got it.

    There are cis and trans versions of 1,2-dimethylcyclopropane. But, within the trans isomer, there are also (S) and (R) enantiomers that are nonsuperimposable (by definition).

    Hopefully I will remember all of this on the midterm
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