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Homework Help: I need help in assigning R/S stereochemistyr

  1. Apr 29, 2007 #1
    (There is no problem statement etc.)

    I am having a very hard time figuring out how to assign R/S stereochemistry on certain compounds. I can't rotate molecules in my head without making mistakes, and so I rotate them on paper.

    Let's take this example:
    http://avogadro.chem.iastate.edu/CHEM331/331FinalKeyF03.pdf [Broken]
    Go to page 6 please, we have to label compounds.

    When a molecule has 2 atoms in the plane, + 1 in the front and 1 in the back, I can rotate them. I keep one atom fixed, usually #2 (4 being the smaller, 1 the largest), and rotate the other 3.

    However, and this is where I need help, I don't know what to do when I have molecules such as the ones on the left, where 2 are in the back and 2 in the front, and none in the plane of the paper/screen.

    How can I rotate those on paper in order to assign R/S stereochemistry?

    Thank you for any help you can give me!

    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Apr 29, 2007 #2
    Actually I found this:
    http://chem.pdx.edu/~wamserc/C334F99/4notes.htm [Broken]

    Last edited by a moderator: May 2, 2017
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