2Stereoisomer Enantiomer Diastereomer Erythro, threo Meso Compound EpimerChiral Molecules With No Chiral Centers
3DefinitionsStereoisomers – compounds with the same connectivity, different arrangement in spaceEnantiomers – stereoisomers that are non-superimposible mirror images; only properties that differ are direction (+ or -) of optical rotationDiastereomers – stereoisomers that are not mirror images; different compounds with different physical properties
15Specifying Configuration (Chirality); Cahn-Ingold-Prelog Notation Specifies the "configuration" at each chiral center, equivalent to "cis-" and "trans-" etc.Abbreviated rulesAssign priorities to groups attached to chiral center according to atomic # (same as Z/E rules)Compare 2nd, 3rd etc. atom from center as necessary, look for first point of differenceMultiple bonds "add up"Determine direction of rotation 1 > 2 > 3 looking with #4 group pointing "away"
16Prioritize Using Cahn-Ingold-Prelog Rules Look at atoms directly attached to chirality centera) higher atomic number = higher priorityb) heavier isotopes = higher priorityIf no difference at first attached atom, move along the chain until the first point of difference.Multiple-bonded atoms are equivalent to the same number of single-bonded atoms.