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 1. Soluble in water 2. Boiling point: very low, about 20 0 C 3. R—O—R bonds: tetrahedral bond angle 4. The Oxygen atom is sp 3 -hybridized

10. Preparation of Ethers

11. Symmetrical ethers R-O-R

12. Mechanism:

13. Examples

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

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

16. tert-Butoxide ionIodomethanetert-Butyl methyl ether

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

18. Alkoxymercuration of Alkenes 1) Reaction

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 S N 2 Ethyl isopropyl etherIsopropyl alcoholIodoethane

23. Mechanism

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

25. 2) Ethers with a tertiary, benzylic, or allylic group react by an S N 1 or E1 E1 reaction tert-Butyl cyclohexyl etherCyclohexanol2-Methylpropene

26. Mechanism:

27. S N 1 reaction

28. Mechanism:

29. Claisen Rearrangement 1) Claisen rearrangement is pecific to allyl aryl ethers, Ar-O-CH 2 CH=CH 2 2) Example: PhenolSodium phenoxideAllyl phenyl ether 0-Allylphenol

30. 3) Mechanism: Transition state