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!

Ochem, name R or S for this? Why?

  1. Feb 26, 2013 #1

    Why is the 2nd chiral carbon of cephalexin molecule R??? I thought the N has first priority, then the Carbon with the double bond to the O would be second (b/c has no H), and the Carbon bonded to the S would be third priority b/c it has a hydrogen, and of course, H is fourth... But then it would be S if that was the case... Why is it R???
  2. jcsd
  3. Feb 28, 2013 #2
    Never mind. Well, not that anyone was going to answer anyway.

    But the chiral carbon in question is bonded to an S and an N. S and N have a greater atomic weight than O. So the H doesn't matter.

    The Carbon bonded to the S and N is second priority.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Threads - Ochem name Date
Naming Compounds Thursday at 1:11 PM
How to calculate new IHD after finding a molecule in IR spec Mar 19, 2017
OChem 2 - LiAlH4 vs NaBH4 - Lab Question Jan 26, 2016
OChem: Synthesis problem Feb 15, 2015
OChem Issue: Tosylation Jan 17, 2015