1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Why is this not a geometric isomer?

  1. Oct 20, 2015 #1

    While I'm fairly sure this question is pretty straight forward, I can't remember why (ii) is not considered a geometric isomer. (The answer is (c)) http://imgur.com/ObccNpv

    Looking at ii I would have thought it to be trans-pent-2-ene due to the ethyl and methyl group either side of the double bond, however it is not and I am not sure why. Would anyone happen to know why this is?

    Thanks :)
  2. jcsd
  3. Oct 20, 2015 #2


    User Avatar

    Staff: Mentor

    Are (i) and (ii) isomers at all?
  4. Oct 20, 2015 #3

    Well, (I) and (II) are not geometric isomers because they are the same compound just mirror images, besides both seem trans to me.
    I II and III can not be geo. (cis-trans) isomers because that is three options.
    III and IV don't make sense because IV is trans so III should be cis but it's weird because its not.

    Sorry that's all I can help with my limited knowledge.
  5. Oct 21, 2015 #4


    User Avatar
    Homework Helper
    Gold Member

    Being mirror images does not necessarily make them the same compound! You probably remember now. :oldsmile:

    The essential is you can swivel it around a vertical axis and i coincides with ii - so it is the same thing. Any bodily movement leading one to coincide with another means it is the same thing. A reflection on the other hand is not a bodily movement.

    I think that identity was the essential point of this excercise. Anything that has the same composition as another thing but is not the same thing is an isomer of it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Threads for geometric isomer
Organic isomer problem