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Chapter 14 Ethers, Epoxides, and Sulfides



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Chapter 14 Ethers, Epoxides, and Sulfides

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    1. Chapter 14 Ethers, Epoxides, and Sulfides Modified from Jo Blackburn Richland College, Dallas, TX Dallas County Community College District ă 2003, Prentice Hall

    2. Chapter 14 2

    3. Chapter 14 3 Structure and Polarity Bent molecular geometry – “water like” Oxygen is sp3 hybridized Tetrahedral angle

    4. Chapter 14 4

    5. Chapter 14 5 Hydrogen Bond Acceptor Ethers cannot H-bond to each other. In the presence of -OH or -NH (donor), the lone pair of electrons from ether forms a hydrogen bond with the -OH or -NH.

    6. Chapter 14 6

    7. Chapter 14 7

    8. Chapter 14 8

    9. Chapter 14 9 Common Names of Ethers Alkyl alkyl ether Current rule: alphabetical order Old rule: order of increasing complexity Symmetrical: use dialkyl, or just alkyl. Examples:

    10. Chapter 14 10 IUPAC Names Alkoxy alkane: use the more complex alkyl group as the root.

    11. Chapter 14 11 Cyclic Ethers Heterocyclic: noncarbon in the ring: oxygen is in ring.

    12. Chapter 14 12

    13. Chapter 14 13 Williamson Synthesis Alkoxide ion + 1? alkyl bromide (or tosylate) (1) form alkoxide (2) SN2 attack of R-X

    14. Chapter 14 14 Phenyl Ethers Phenoxide ions are easily produced for use in the Williamson synthesis. Phenyl halides or tosylates cannot be used in this synthesis method.

    15. Chapter 14 15 Alkoxymercuration-Demercuration Use mercuric acetate with an alcohol to add RO-H to a double bond and form the Markovnikov product.

    16. Chapter 14 16

    17. Chapter 14 17

    18. Chapter 14 18

    19. Chapter 14 19

    20. Chapter 14 20 Cleavage of Ethers Ethers are unreactive toward base, so make good solvents Protonated ethers can undergo substitution reactions with strong acids. Alcohol leaving group is replaced by a halide. Reactivity: HI > HBr >> HCl =>

    21. Chapter 14 21 Mechanism for Cleavage

    22. Chapter 14 22

    23. Chapter 14 23

    24. Chapter 14 24

    25. Chapter 14 25

    26. Chapter 14 26

    27. Chapter 14 27 Sulfides (Thioethers) R-S-R, analog of ether Name like ethers, replacing “sulfide” for “ether” in common name, or “alkylthio” for “alkoxy” in IUPAC system. More reactive than ethers!

    28. Chapter 14 28 Thiols and Thiolates R-SH about same acidity as phenols.

    29. Epoxides Synthesis and Reactivity

    30. Chapter 14 30

    31. Chapter 14 31 Naming Epoxides

    32. Chapter 14 32

    33. Chapter 14 33 Synthesis of Epoxides Peroxyacid epoxidation

    34. Chapter 14 34 Synthesis of Epoxides

    35. Chapter 14 35 Synthesis of Epoxides

    36. Chapter 14 36

    37. Chapter 14 37 Ring Opening in Acid more reactive than ethers due to ring-strain Trans diol formed in water solvent.

    38. Chapter 14 38

    39. Chapter 14 39 Ring Opening in Base Epoxide’s high ring strain makes it susceptible to nucleophilic attack.

    40. Chapter 14 40 Epoxide Opening in Base aqueous hydroxide, a trans 1,2-diol is formed. With alkoxide in alcohol, a trans 1,2-alkoxy alcohol is formed.

    41. Chapter 14 41 Write out the Mechanism(s)

    42. Chapter 14 42 Orientation of Epoxide Opening Base attacks the least hindered carbon.

    43. Reaction with Grignard and R-Li Strong base opens the epoxide ring by attacking the less hindered carbon.

    44. Chapter 14 44 End of Chapter 14

    45. Chapter 14 45 For Wednesday 32, 34, 37, 39, 42

    46. Chapter 14 46

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