1. Stereochemistry

2. Stereochemistry: – The study of the three-dimensional structure of molecules Structural (constitutional) isomers: – same molecular formula but different bonding sequence Stereoisomers: – same molecular formula, same bonding sequence, different spatial orientation

3. The properties of many drugs depends on their stereochemistry: (S)-ketamine (R)-ketamine anesthetichallucinogen

4. Optical Isomerism Optical Activity The property of the substance to rotate the plane of the plane-polarized light is known as optical activity. - Dextro-rotatory (+) - Laevorotatory (- ) Necessary condition: Molecule should be dissymmetric. Example: Biphenyl 2, 2’ – disulphonic acid

5. Enantiomers Enantiomers are defined as the isomers where molecular Structures are mirror images of each other and which rotate the plane of the polarized light equally but in opposite directions. - Properties of enantiomers Chirality is the necessary and sufficient condition for the existence of enantiomers.

6. Chiral vs. Achiral Example: Identify the following molecules as chiral or achiral.

7. Diastereomers Pair of molecules with two or more different chiral carbon atoms which are neither identical nor non- superimposable mirror images of each other.

8. Enantiomers Enantiomers nonsuperimposible mirror images

9. Meso Compound A compound with two or more asymmetric carbon atoms but also having a plane of symmetry (a mirror plane) is called the Meso compound.

10. Meso Compound Meso Compound Internal Plane of Symmetry Optically Inactive

11. Absolute Configuration

12. Assign Priority to each Group on Asymmetric Center Example priorities: I > Br > Cl > S > F > O > N > 13 C > 12 C > 3 H > 2 H > 1 H

13. Lactic Acid

14. C.I.P. Priorities

15. (R) and (S) Nomenclature The two enantiomers of alanine are: Natural alanineUnnatural alanine (S)-alanine(R)-alanine

16. (R) and (S) Nomenclature CH(CH 3 ) 2 > CH 2 CH 2 Br > CH 3 CH 2 4 2 3 1

17. Fischer Projections

18. Assigning Absolute Configuration to Fischer Projections

19. Fischer Projections with 2 Chiral Centers

20. Tartaric Acids

21. 2,3,4-trichlorohexane How many stereoisomers?

22. n = 3; 2 n = 8

23. A Carbohydrate

24. Reactions that Generate Chirality Centers Hydrogenation, syn

25. Bromination Trans is formed exclusively No Meso is formed (cis)