Chapter 7: Configurations

A stereocenter—typically a carbon bonded to four different groups—creates molecular handedness, leading to R/S configurations. Students learn to identify stereocenters, assign atomic priorities based on the Cahn-Ingold-Prelog system, and determine R or S using either mental rotation or a shortcut switch technique. The chapter then introduces the naming of stereoisomers, including (R)/(S) and (E)/(Z) designations, with E/Z nomenclature improving on traditional cis/trans for double bonds. Drawing and interpreting enantiomers and diastereomers is covered, highlighting that enantiomers are nonsuperimposable mirror images, while diastereomers differ at only some stereocenters. The chapter explains meso compounds, which possess stereocenters but are superimposable on their mirror images due to internal symmetry. Students also learn Fischer projections, a standardized way to depict multiple stereocenters efficiently. The chapter concludes by clarifying that optical activity (dextrorotation [+] or levorotation [−]) is independent of R/S configuration and can only be determined experimentally. Mastery of these concepts is crucial for predicting reaction outcomes, naming compounds correctly, and understanding the behavior of chiral molecules.