Stereochemistry determines biological activity, physical properties, and mechanism outcome; the same connectivity can produce molecules with dramatically different behavior in space.
Identify stereogenic centers and distinguish chiral, achiral, meso, and racemic situations.
Assign R/S configurations using the Cahn-Ingold-Prelog priority rules.
Classify pairs of molecules as identical, enantiomers, diastereomers, or constitutional isomers.
Interconvert wedge-dash drawings, Fischer projections, and simple conformational views without changing configuration.
Checkpoint Questions
Q: What is the relationship between (2R,3R)-2,3-butanediol and (2S,3S)-2,3-butanediol?
A: They are enantiomers because every stereocenter is inverted and the two molecules are mirror images.
Q: Why is meso tartaric acid achiral?
A: It contains stereocenters, but an internal mirror plane makes the whole molecule superimposable on its mirror image.