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Chapter 18

Chapter 18. Ethers and Epoxides; Thiols and Sulfides. Ethers. Definition: Two organic groups bonded to the same oxygen atom Examples:. Diethyl ether. Methyl phenyl ether (Anisole). Tetrahydrofuran (cyclic ether). Naming of Ethers. There are two ways to name it:

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Chapter 18

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  1. Chapter 18 Ethers and Epoxides; Thiols and Sulfides

  2. Ethers • Definition: Two organic groups bonded to the same oxygen atom • Examples: Diethyl ether

  3. Methyl phenyl ether (Anisole) Tetrahydrofuran (cyclic ether)

  4. Naming of Ethers There are two ways to name it: • Identifying the two organic substituents and adding the word ether Dimethyl ether

  5. Tert-Butyl methyl ether Ethyl-phenyl ether

  6. If other functional groups are present, the ether part is considered an alkoxy substituent. Tert-butoxy butane Para-ethoxy methoxy benzene

  7. 1-methoxy-cyclohexene 4-tert-Butoxy-1-cyclohexene

  8. Isopropoxy cyclohexane p-dimethoxybenzene

  9. Physical Properties • Soluble in water • Boiling point: very low, about 200C • R—O—R bonds: tetrahedral bond angle • The Oxygen atom is sp3-hybridized

  10. Preparation of Ethers

  11. Symmetrical ethers R-O-R

  12. Mechanism:

  13. Examples

  14. Symmetrical ethersR-O-R’ • The Williamson Ether Synthesis:

  15. Examples α-D-Glucose Α-D-Glucose pentamethyl ether

  16. tert-Butoxide ion Iodomethane tert-Butyl methyl ether

  17. Methoxide ion 2-Chloro-2-methylpropane 2-Methylpropene

  18. 1) Reaction • Alkoxymercuration of Alkenes

  19. 2. Mechanism

  20. 3. Examples Styrene 1-Methoxy-1-phenyethane

  21. Reaction of Ethers

  22. Acidic Cleavage 1) Ethers with primary and secondary alkyl groups react by an SN2 Ethyl isopropyl ether Isopropyl alcohol Iodoethane

  23. Mechanism

  24. Examples: Bromoethane Ethyl phenyl ether Phenol 2-Ethoxypropanoic acid Iodoethane Lactic acid

  25. 2) Ethers with a tertiary, benzylic, or allylic group react by an SN1 or E1 E1 reaction tert-Butyl cyclohexyl ether Cyclohexanol 2-Methylpropene

  26. Mechanism:

  27. SN1 reaction

  28. Mechanism:

  29. 1) Claisen rearrangement is pecific to allyl aryl ethers, Ar-O-CH2CH=CH2 • Claisen Rearrangement 2) Example: Phenol Sodium phenoxide Allyl phenyl ether Allyl phenyl ether 0-Allylphenol

  30. 3) Mechanism: Transition state

  31. sECTION 18.7

  32. SECTION 18.8

  33. SECTION 18.9

  34. SECTION 18.10

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