Which of the following correctly describes the relationship between the R,S system and the +/− system associated with optically active compounds?
A) All R enantiomers are (+).
B) All S enantiomers are (+).
C) No S enantiomers are (+), but some R enantiomers are (−).
D) There is no general relationship between the R,S designations and the +/− designations.

Question

Quizplus · Accepted Answer

The R,S system and the +/− system are two different ways of designating the configuration of optical isomers. The R,S system determines the configuration by assigning priorities to the four substituents on the chiral center based on the Cahn-Ingold-Prelog rules. The +/− system, on the other hand, designates the configuration based on the direction in which the molecule rotates polarized light: (+) means that the molecule rotates the plane of polarized light clockwise and (−) means it rotates it counterclockwise. While there is a correlation between the R,S system and the +/− system in some cases, there is no general relationship between the two. Therefore, the best choice is D.

Which of the Following Correctly Describes the Relationship Between the R,S