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Understanding Dehydration and Elimination Reactions in Alcohols

Explore the mechanisms and procedures involved in Dehydration and Elimination Reactions of Alcohols to form alkenes. Learn about leaving group mechanisms, E1 reactions, isotope effects, elimination procedures, and Baeyer Unsaturation Tests.

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Understanding Dehydration and Elimination Reactions in 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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