Molecule chirality: R/S vs r/s

User 9b067d2e85

27-02-2014 23:28:57

I was looking at the StereoCheckUtility to identify unspecified stereo centers in a molecule and found:


getNotAbsoluteRSChiralCenters(mol)


getUndefinedrsChiralCenters(mol)


I'm curious exactly what the difference is between R/S and r/s. Do I need to check for both?


http://www.chemaxon.com/jchem/doc/dev/java/api/chemaxon/checkers/StereoCheckUtility.html


 


Thanks.

ChemAxon abe887c64e

28-02-2014 08:46:51

Hi Daniel,


R/S signs describe the absolute tetrahedral stereo configuration of an atom with four different substituent.


r/s signs describe the relative tetrahedral stereo configuration of an atom without four different substituents. In this case there must be at least two tetrahedral stereo center in the molecule, and the relation of them to each other is notified by r/s.


Please see the attached examples.


Best regards


Krisztina