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Stereoisomers and Molecular Recognition Isomerism Same number, kind of atoms Isomers Different connectivity Same connectivity but different spatial arrangement Stereoisomers Structural Isomers Non-superimposable mirror images Geometric Isomers e.g., cis,trans Optical Isomers Conformational Isomers Interconvert by sigma bond rotation Optical Isomerism Mirror Images Mirror QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Can Mirror Images Be Superimposed? QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. superimposable mirror images (not optical isomers) QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. nonsuperimposable mirror images (optical isomers) Optical Isomers Result When Center Carbon Is Chiral (Has 4 Different Substituents) QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Same density, boiling point, and other physical properties. BUT, different reactivities with other chiral molecules. Lactic Acid Optical Isomers of Lactic Acid (Investigate This #5.62) QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Mirror Images, Non-Superimposable Optical Isomer of Glucose? (Check This #5.64) On one hexagon On second 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-CH2- group 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 The Polarimeter animation of polarimetry Investigate This #5.59 #1 no sample #2 no sample #3 water #4 corn syrup filters polarizing filters positioned to allow maximum light through polarizing filters polarizing filters polarizing filters positioned to allow ~no positioned to allow ~no positioned to allow ~no light through light through light through (top filter (no change from #2) has been rotated from #2) Molecular Recognition in Drug Therapy Dopamine in Neurotransmission basal ganglia produce dopamine Neuron QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. No Dopamine = No Nerve Signals Parkinson’s Disease: Loss of Brain Dopamine dopamine receptors normal movement movement disorders normal movement restored normal subject QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. l-dopa therapy replaces missing dopamine Parkinson patient Parkinson patient Parkinson’s Disease: Loss of Brain Dopamine dopamine receptors normal movement movement disorders normal movement restored normal subject QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. L-dopa therapy replaces missing dopamine Parkinson patient Parkinson patient Optical Isomerism in DOPA QuickTime™ and a TIFF (LZW ) decompressor are needed to see this picture. QuickTime™ and a TIFF (LZW) decompressor are needed to see this pict ure. DOPA L-DOPA QuickTime™ and a TIFF (LZW ) decompressor H are needed to see this picture. Qu i ck Ti m e ™ an d a TI F F ( LZ W) d ec om pr es so r ar e n ee de d t o s ee t h is pi ct u re . D-DOPA enzyme that converts DOPA to dopamine works only with this isomer pharmaceutical syntheses are designed to avoid making this isomer Optical Isomerism in DOPA QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. 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 Molecular Recognition in Vision Cis-Trans Isomerism in Vision QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Rxn Occurs in Rhodopsin Rhodopsin = cis-retinal + opsin (protein) QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Cis-Trans Isomerism and Vision photoisomerization of rhodopsin photoisomerization of rhodopsin (same animation, alternate site)