Organic Chemistry 4 th Edition Paula Yurkanis Bruice Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall Chapter 5 Stereochemistry The Arrangement of Atoms in Space; The Stereochemistry of Addition Reactions Isomers Nonidentical compounds having the same molecular formula Cis-Trans Isomers Achiral compounds have superimposable mirror images Chiral compounds have nonsuperimposable mirror images Enantiomers nonsuperimposable mirror-image molecules Drawing Enantiomers Perspective formula Fischer projection A stereocenter (stereogenic center) is an atom at which the interchange of two groups produces a stereoisomer Naming Enantiomers Rank the groups (atoms) bonded to the chirality center The R,S system of nomenclature Orient the lowest priority (4) away from you Clockwise = R configuration Counterclockwise = S configuration Naming from the Perspective Formula 1 2 3 4 1. Rank the groups bonded to the asymmetric carbon 2. If the group (or atom) with the lowest priority is bonded by hatched wedge,