Chapter 9: Stereochemistry Things to know: What are enantiomers? What is a chiral molecule? You should be able to identify all the chiral centers in a given molecular structure. What is optical activity? What kinds of compounds exhibit optical activity? What does levorotatory (-) and dextrorotatory (+) mean? What can you say about the optical rotation of a pair of enantiomers? You should be able to assign R and S configuration for each chiral center. Also, given that a chiral center is R or S, you should be able to draw a structure to represent this. What are diasteromers? What is the minimum requirement for a compound to exist as diastereomers? (it should have at least two chiral centers). You should be able to decide whether a pair of compounds are enantiomers or diastereomers. Also, given the structure of a molecule, you should be able to draw its enantiomer and diastereomers. What are meso compounds? What are racemic mixtures? What can you say about the optical activity of meso compounds and racemic mixtures? Why does the reaction of 1-butene with HBr result in a racemic mixture? What is prochirality? Know how to determine the Re or Si face of a prochiral compound.