The S and R labels are applied to enantiomers, pairs of molecules that demonstrate this concept.  
Le Bel and van't Hoff took advantage of this property to help determine the tetrahedral structure of carbon compounds.  It is critical in pharmacology as it explains why only some methyl-dopa and ibuprofen molecules are effective.  It also occurs in simpler molecules such as 2-butanol. The S and R labels are applied to enantiomers, pairs of molecules that demonstrate this concept.  FTP, identify this term that indicates the molecular version of left- and right-handedness.
Le Bel and van't Hoff took advantage of this property to help determine the tetrahedral structure of carbon compounds.  
chirality