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SN1 Reaction

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SN1 Reaction

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    1. Chapter 6 1 SN1 Reaction Unimolecular nucleophilic substitution. Two step reaction with carbocation intermediate. Rate is first order in the alkyl halide, zero order in the nucleophile. Racemization occurs. =>

    2. Chapter 6 2

    3. Chapter 6 3

    4. Chapter 6 4

    5. Chapter 6 5

    6. Chapter 6 6

    7. Chapter 6 7

    8. Chapter 6 8

    9. Chapter 6 9 SN1 Mechanism (2)

    10. Chapter 6 10

    11. Chapter 6 11

    12. Chapter 6 12

    13. Chapter 6 13

    14. Chapter 6 14

    15. Chapter 6 15

    16. Chapter 6 16

    17. Chapter 6 17

    18. Chapter 6 18

    19. Chapter 6 19

    20. Chapter 6 20 Rates of SN1 Reactions Structure of Carbocation 3 > 2 > 1 >> CH3X Order follows stability of carbocations (opposite to SN2) More stable ion requires less energy to form Stability of leaving group, faster reaction (like SN2) Polar protic solvent best: solvates leaving group ions strongly (hydrogen bonding) Solvates carbocation intermediate (hydrogen bonding)

    21. Chapter 6 21

    22. Chapter 6 22

    23. Chapter 6 23

    24. Chapter 6 24

    25. Chapter 6 25

    26. Chapter 6 26

    27. Chapter 6 27

    28. Chapter 6 28

    29. Chapter 6 29

    30. Chapter 6 30

    31. Chapter 6 31

    32. Chapter 6 32 Stereochemistry of SN1 Racemization: inversion and retention

    33. Chapter 6 33

    34. Chapter 6 34

    35. Chapter 6 35

    36. Chapter 6 36

    37. Chapter 6 37

    38. Chapter 6 38

    39. Chapter 6 39

    40. Chapter 6 40

    41. Chapter 6 41 SN2 or SN1? Primary or methyl Strong nucleophile Polar aprotic solvent Rate = k[halide][Nuc] Inversion at chiral carbon No rearrangements Tertiary Weak nucleophile (may also be solvent) Polar protic solvent Rate = k[halide] Racemization of optically active compound Rearranged products =>

    42. Chapter 6 42 Rearrangements Carbocations can rearrange to form a more stable carbocation. Hydride shift: H- on adjacent carbon bonds with C+. Methyl shift: CH3- moves from adjacent carbon if no Hs are available. =>

    43. Chapter 6 43 Hydride Shift

    44. Chapter 6 44 Methyl Shift

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