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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. C - C. X. 3 ways to break 2 bonds. 1. Concerted (x and y leave same time) 2. X leaves first 3. Y leaves first. Leaving Group. E1 Reaction. R-X. R + + X -. Alkene + H +.

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

  4. Leaving Group

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

  6. E1 1 bond at a time Elimination

  7. R+ SN1 E1 Rearrangement Substitution Elimination

  8. SN1 E1

  9. Dehydrohalogenation X C - C H Strong base

  10. What is the mechanism of dehydrohalogentation? C-D bond stronger than C-H bond.

  11. Isotope Effect NaOEt NaOEt kH/kD = 7

  12. Isotope effect shows that C-H bond broken in the transition state.

  13. Element Effect Change Element I > Br > Cl

  14. SYN vs. ANTI Elimination Same Side Opposite Side

  15. Transition State Energy Starting Material Product

  16. E 2 2 Bonds at a time Elimination

  17. Procedure

  18. Put cyclohexanol and sulfuric acid in round bottom flask • Fractional Distillation (steam distillation) collect distillate 80-85o • Dry product with K2CO3 • 4. Distill

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

  20. Baeyer Unsaturation Tests Potassium Permanganate KMnO4

  21. Bromine and Cyclohexene

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