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Stereochemistry

Stereochemistry

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Stereochemistry

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  1. Stereochemistry 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.

  2. 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

  3. 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

  4. Plane-Polarized Light

  5. Plane-Polarized Light through an Achiral Compound

  6. Plane-Polarized Light through a Chiral Compound

  7. Polarimeter Measures Optical Rotation

  8. 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

  9. 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

  10. Chirality CenterCarbon has four different groups attached

  11. Enantiomersnonsuperimposible mirror images

  12. Enantiomeric Excess(Optical Purity)

  13. Biological Activity

  14. SSRI Efficacy depends on Stereochemistry

  15. Absolute Configuration

  16. Assign Priority to each Group on Asymmetric Center

  17. Lactic Acid

  18. C.I.P. Priorities

  19. Fischer Projections

  20. Assigning Absolute Configuration to Fischer Projections

  21. Rotation of the Projection 90oReverses Absolute Configuration

  22. DiastereomersStereoisomers That Are Not Mirror Images

  23. Fischer Projections with 2 Chiral Centers

  24. 2 Chiral Centers4 Stereoisomers

  25. Identical, Enantiomers or Diastereomers?

  26. Tartaric Acids

  27. Racemic Mixture

  28. Meso CompoundInternal Plane of SymmetryOptically Inactive

  29. 2,3,4-trichlorohexaneHow many stereoisomers?

  30. n = 3; 2n = 8

  31. A Carbohydrate

  32. Internal Planes of Symmetry

  33. Asymmetric Centers on Rings

  34. Allenes can be Chiral

  35. Mycomycin, an antibiotic

  36. Reactions that Generate Chirality Centers Hydrogenation, syn

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

  38. Bromonium Ion is Opened Equally from Both Sides

  39. trans alkene + anti addition = MESO

  40. cis Alkene + anti addition =racemic mixture

  41. Brominations Often Generate Asymmetric Centers

  42. Asymmetric Center is Generated Racemic Mixture Formed

  43. Asymmetric Induction

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

  45. Relevance of Stereochemistry

  46. One-step synthesis

  47. a-(p-isobutylphenyl)propionic acid

  48. Model of Thalidomide