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Stereochemistry

Stereochemistry. Dr. A. G. Nikalje Dept. Of Pharmaceutical Chemistry. Stereochemistry refers to the 3-dimensional properties and reactions of molecules. It has its own language and terms that need to be learned in order to fully communicate and understand the concepts.

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Stereochemistry

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  1. Stereochemistry Dr. A. G. Nikalje Dept. Of Pharmaceutical Chemistry

  2. Stereochemistry refers to the 3-dimensional properties and reactions of molecules. • It has its own language and terms that need to be learned in order to fully communicate and understand the concepts. • Chiral carbon, optical activity, R/S forms

  3. Definitions • Stereoisomers – compounds with the same connectivity, different arrangement in space • Enantiomers – stereoisomers that are non- superimposible mirror images; only properties that differ are direction (+ or -) of optical rotation • Diastereomers – stereoisomers that are not mirror images; different compounds with different physical properties

  4. More Definitions • Asymmetric center – sp3 carbon with 4 different groups attached • Optical activity – the ability to rotate the plane of plane –polarized light • Chiral compound – a compound that is optically active (achiralcompound will not rotate light) • Polarimeter – device that measures the optical rotation of the chiral compound

  5. Plane-Polarized Light

  6. Plane-Polarized Light through an Achiral Compound

  7. Plane-Polarized Light through a Chiral Compound

  8. Polarimeter Measures Optical Rotation

  9. Specific Rotation, [α] [α] = α / cl a = observed rotation c = concentration in g/mL l = length of tube in dm Dextrorotary designated as d or(+), clockwise rotation Levorotary designated as l or (-), counter- clockwise rotation

  10. Specific Rotations of some Common Organic Compounds Compound [a] # * centers Penicillin V +233.0 3 Sucrose +66.5 10  Camphor +44.3 2 MSG +25.5 1 Cholesterol -31.3 8 Morphine -132.0 5

  11. Chirality CenterCarbon has four different groups attached

  12. Enantiomersnonsuperimposible mirror images

  13. Enantiomeric Excess(Optical Purity)

  14. Biological Activity

  15. SSRI Efficacy depends on Stereochemistry

  16. Absolute Configuration

  17. Assign Priority to each Group on Asymmetric Center

  18. Lactic Acid

  19. C.I.P. Priorities

  20. Fischer Projections

  21. Assigning Absolute Configuration to Fischer Projections

  22. Rotation of the Projection 90oReverses Absolute Configuration

  23. DiastereomersStereoisomers That Are Not Mirror Images

  24. Fischer Projections with 2 Chiral Centers

  25. 2 Chiral Centers4 Stereoisomers

  26. Identical, Enantiomers or Diastereomers?

  27. Tartaric Acids

  28. Racemic Mixture

  29. Meso CompoundInternal Plane of SymmetryOptically Inactive

  30. 2,3,4-trichlorohexaneHow many stereoisomers?

  31. n = 3; 2n = 8

  32. A Carbohydrate

  33. Internal Planes of Symmetry

  34. Asymmetric Centers on Rings

  35. Allenes can be Chiral

  36. Mycomycin, an antibiotic

  37. Reactions that Generate Chirality Centers Hydrogenation, syn

  38. BrominationTrans is formed exclusivelyNo Meso is formed (cis)

  39. Bromonium Ion is Opened Equally from Both Sides

  40. trans alkene + anti addition = MESO

  41. cis Alkene + anti addition =racemic mixture

  42. Brominations Often Generate Asymmetric Centers

  43. Asymmetric Center is Generated Racemic Mixture Formed

  44. Asymmetric Induction

  45. Preparation of (L)-Dopafor Treatment of Parkinson’s

  46. Relevance of Stereochemistry

  47. One-step synthesis

  48. a-(p-isobutylphenyl)propionic acid

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