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Dehydration of Alcohols

Dehydration of Alcohols. Elimination Reactions. Y. C - C. X. To make C=C need to eliminate X, Y. Y. 3 ways to break 2 bonds. C - C. X. 1. Concerted (x and y leave same time) 2. X leaves first 3. Y leaves first. Leaving Group. Mechanism. Mechanism. E1 Reaction. R-X.

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Dehydration of Alcohols

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  1. Dehydration of Alcohols

  2. Elimination Reactions Y C - C X To make C=C need to eliminate X, Y.

  3. Y 3 ways to break 2 bonds C - C X 1. Concerted (x and y leave same time) 2. X leaves first 3. Y leaves first

  4. Leaving Group

  5. Mechanism

  6. Mechanism

  7. E1 Reaction R-X R+ + X- Alkene + H+

  8. E1 1 bond at a time Elimination

  9. R+ SN1 E1 Rearrangement Substitution Elimination

  10. E1 SN1 SN1 E1

  11. Dehydrohalogenation X C - C H Strong base

  12. What is the mechanism of dehydrohalogentation? Isotope Effects C-D bond stronger than C-H bond.

  13. Isotope Effect NaOEt NaOEt kH/kD = 7

  14. Bond Broken in Transition State Isotope effect shows that C-H bond broken in the transition state.

  15. Element Effect Change Element I > Br > Cl

  16. SYN vs. ANTI Elimination Same Side Opposite Side

  17. E2 Animation

  18. Transition State Energy Starting Material Product

  19. E 2 2 Bonds at a time Elimination

  20. Procedure

  21. Put cyclohexanol and sulfuric acid in round bottom flask Fractional Distillation (steam distillation) collect distillate 80-85o Procedure

  22. Dry product with K2CO3

  23. Distill

  24. Distil immiscible liquids PT = PA + PB (Steam Distillation)

  25. Baeyer Unsaturation Tests Potassium Permanganate KMnO4

  26. Baeyer Unsaturation Tests

  27. Bromine Addition

  28. Bromine and Cyclohexene

  29. - Bromonium Ion - + Br + Br Br Br

  30. Bromonium Ion Intermediate

  31. Mechanism Br -

  32. Animation

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