1 / 34

Chapter 16 & 17 Discussion

Chapter 16 & 17 Discussion. Meso = identical. Endo and exo are meaningless without substitutents to provide frame of reference. diene. dienophile. Recognize that this is a Diels Alder reaction by the diene and dienophile (on the right). 2) Draw a cyclohexene ring.

grady
Download Presentation

Chapter 16 & 17 Discussion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 16 & 17 Discussion

  2. Meso = identical Endo and exo are meaningless without substitutents to provide frame of reference

  3. diene dienophile Recognize that this is a Diels Alder reaction by the diene and dienophile (on the right) 2) Draw a cyclohexene ring 3) Build models of the possible isomers that could result from the cycloaddition 4) Use resonance to help predict regioisomer 5) Temperature for endo/exo preference.

  4. endo exo 3) Build models of the possible isomers that could result from the cycloaddition 4) Use resonance to help predict regioisomer 5) Temperature for endo/exo preference.

  5. Endo and exo + enantiomer + enantiomer Exo (thermodynamic product) Endo (kinetic product)

  6. ? Recognize that this is a Diels Alder reaction by the diene and dienophile (on the right) 2) Draw a cyclohexene ring 3) Build models of the possible isomers that could result from the cycloaddition 4) Use resonance to help predict regioisomer 5) Temperature for endo/exo preference.

  7. Four possible regioisomers and diastereomers (+ enantiomers)

  8. Resonance contributors show which regioisomers will form

  9. Regiochemistry is established. How about endo or exo?

  10. ?

  11. No meta.

  12. Problem:Diels-Alder Reactants?

  13. Flat, cyclic, conjugated pi system and 4n + 2 pi electrons

  14. Aromatic if 2, 6, 10, 14, 18 pi electrons….. Anti-aromatic if 4, 8, 12, 16, ….. pi electrons If neither then not aromatic or anti-aromatic. Anti-aromatic more stable than expected. Anti-aromatic – less stable and likely will not form at all.

  15. Cyclopropenyl anion 4 pi electrons. Antiaromatic

  16. Aromatic?

  17. Cyclopentadienyl anion 6 pi electrons, aromatic

  18. Aromatic?

  19. Azulene Yarrow chamomile 10 pi electrons aromatic Lactariusazulene

  20. Naphthalene aromatic : cyclic, 10 electrons, flat, conjugated

  21. naphthalene Azulene Why is naphthalene nonpolar and azulene polar?

  22. Aromatic, anti-aromatic or neither?

  23. Aromatic, anti-aromatic or neither? 8 pi electrons Depends on conformation. If flat and fully conjugated, antiaromatic!!!! Lower energy conformation (than anti-aromatic) is not flat

More Related