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: R/S Configuration and Identical Compounds

  1. Feb 25, 2014 #1
    1. The problem statement, all variables and given/known data

    Hello, so I think I've been looking at this problem way too long, and I'm going no where with it. It is in my attached picture, because it is easier to draw than write out on here.
    The key says these two are identical compounds, meaning they should have the same configuration.
    But, I keep on getting R for the first and S for the second.
    I got R for the first by switching the configuration since the 4th one should be going away, but it is rather coming towards me. I got S by following the priorities. Would someone be able to tell me where I am going wrong, please? I am very confused.

    Attached Files:

  2. jcsd
  3. Feb 25, 2014 #2
    Am I drawing all the priorities correctly?
    I keep looking at my solution manual and I'm getting all opposite answers for all the questions :(. Is there something crucial I'm missing here?
    Last edited: Feb 25, 2014
  4. Mar 2, 2014 #3


    User Avatar
    Science Advisor

    The priorities of CH2CH2OH and CH2CH3 should be 3 and 4, respectively as O has higher priority than H. You seem to have assigned them the other way round.
    To assign R or S to the structures, you have to rotate the molecule so that substituent 4 lies behind the central C and then determine the direction from 1 over 2 to 3.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted