1. Stereoisomers and Molecular Recognition

2. Isomerism Same number, kind of atoms Different connectivity Non-superimposable mirror images Same connectivity but different spatial arrangement e.g., cis,trans Isomers Structural Isomers Stereoisomers Geometric Isomers Optical Isomers Conformational Isomers Interconvert by sigma bond rotation

3. Optical Isomerism

4. Mirror Images Mirror

5. superimposable mirror images (not optical isomers) nonsuperimposable mirror images (optical isomers) Can Mirror Images Be Superimposed?

6. Optical Isomers Result When Center Carbon Is Chiral (Has 4 Different Substituents) Same density, boiling point, and other physical properties. BUT, different reactivities with other chiral molecules.

7. Lactic Acid

8. Optical Isomers of Lactic Acid (Investigate This #5.62) Mirror Images, Non-Superimposable

9. Optical Isomer of Glucose? (Check This #5.64) On one hexagon Put a colored dot at one apex to represent ring O Put a different colored dot at each apex where -OH is oriented toward you Put an “X” at apex with HO-CH 2 - group On second hexagon Make mirror image of the first hexagon Are the hexagons superimposable so that all dots of same color match? Yes = same molecule No = optical isomers

10. The Polarimeter animation of polarimetry

11. Investigate This #5.59 no sample polarizing filters positioned to allow maximum light through water polarizing filters positioned to allow ~no light through (no change from #2) corn syrup polarizing filters positioned to allow ~no light through (top filter has been rotated from #2) filters no sample polarizing filters positioned to allow ~no light through #1 #2 #3 #4

12. Molecular Recognition in Drug Therapy

13. Dopamine in Neurotransmission Neuron basal ganglia produce dopamine No Dopamine = No Nerve Signals

14. Parkinson’s Disease: Loss of Brain Dopamine l -dopa therapy replaces missing dopamine normal movement movement disorders normal movement restored normal subject Parkinson patient dopamine receptors

15. Parkinson’s Disease: Loss of Brain Dopamine L -dopa therapy replaces missing dopamine normal movement movement disorders normal movement restored normal subject Parkinson patient dopamine receptors

16. Optical Isomerism in DOPA DOPA L -DOPA H D -DOPA enzyme that converts DOPA to dopamine works only with this isomer pharmaceutical syntheses are designed to avoid making this isomer

17. Optical Isomerism in DOPA

18. Other Optical Isomers in Drug Therapy Penicillin Reacts with one optical isomer of alanine found in bacteria Does not react with other optical isomer found in humans Thalidomide One optical isomer effective against nausea (morning sickness) Other optical isomer causes birth defects Many drugs are mixtures of optical isomers - BOTH isomers must be tested for safety

19. Molecular Recognition in Vision

20. Cis-Trans Isomerism in Vision

21. Rxn Occurs in Rhodopsin Rhodopsin = cis-retinal + opsin (protein)

22. Cis-Trans Isomerism and Vision photoisomerization of rhodopsin photoisomerization of rhodopsin (same animation, alternate site)