1. Ethers Ethers are compounds with the general formula: R-O-R’
symmetrical ethers: R = R’
unsymmetrical ethers: R = R’
two lone pairs of electrons on oxygen
sp3 hybrid oxygen atom
bent molecular geometry

2. Ethers Ethers are commonly used as solvents in organic reactions.
Polar molecules
no hydrogen bonding between ether molecules
lower BP than comparable alcohols
serves as hydrogen bond acceptor in the presence of alcohols, amines, or carboxylic acids

3. Nomenclature of Ethers
Common Names:
Name the two alkyl groups and add the word ether
alphabetical order
in order of increasing complexity
use prefix “di” to indicate both alkyl groups are identical
if only one alkyl group is described in name, it implies the ether is symmetrical OR

4. Nomenclature of Ethers
Examples of Common Names
CH3CH2OCH3 methyl ethyl ether
CH3CH2OCH2CH3 diethyl ether or ethyl ether

5. Ethers IUPAC Names (Alkoxy alkane) : Ethers names as alkoxy alkanes
Use the more complex alkyl group as the base name
The other alkyl group is named as an alkoxyl group
Examples
CH3CH2OCH3 methoxyethane
CH3CH2OCH2CH3 ethoxyethane

6. Ethers
Example: Name the following ethers.

7. Ethers Example: Draw the following compounds. Methoxycyclopentane
Ethyl t-butyl ether
Chloromethyl methyl ether
(1R, 2R)-2-methoxycyclohexanol

8. Nomenclature of Ethers
Cyclic ethers are heterocyclic compounds:
compounds containing a ring in which one or more ring atoms is an element other than carbon
Epoxide (oxirane):
three membered cyclic ether
Ethylene oxide
oxirane
epichlorohydrin
cyclohexene oxide

9. Nomenclature of Ethers
Furan :
a five-membered aromatic cyclic ether
Tetrahydrofuran (oxolane):
saturated, five-membered cyclic ether

10. Nomenclature of Ethers
Pyran (Oxane):
an unsaturated, six-membered cyclic ether
Dioxane:
heterocyclic ether with two oxygen atoms in a six-membered ring
1,4-dioxane

11. Synthesis of Ethers Williamson Ether Synthesis
SN2 attack of an alkoxide ion on an unhindered methyl or primary alkyl halide or tosylate

12. Synthesis of Ethers Alkoxymercuration-Demercuration:
formation of Markovnikov ether from an alkene
“anti” addition to the double bond
Reagents:
(1) Hg(OAc)2, ROH
(2) NaBH4 R

13. Synthesis of Ethers
Examples:

14. Synthesis of Ethers Epoxidation of Alkenes
formation of an epoxide from an alkene using a peroxyacid
Reagents:
MCPBA
CH3CO3H
Retains stereochemistry of C=C

15. Synthesis of Ethers
Example:

16. Synthesis of Ethers Base-Promoted Cyclization of Halohydrins
formation of epoxides from halohydrin via internal SN2 attack of an alkoxide ion on an adjacent carbon containing a halogen
Reagents:
NaOH (aq)

17. Synthesis of Ethers
Example:

18. Reactions of Ethers Autoxidation of Ethers:
spontaneous oxidation of ethers to hydroperoxides and dialkyl peroxides in the presence of atmospheric oxygen
Hydroperoxides and dialkyl peroxides are highly explosive
do not distill to dryness
use ether promptly
test old cans of ether before use

19. Reactions of Ethers Acid-Catalyzed Ring Opening of Epoxides
SN2 attack of water or alcohol molecule on a protonated epoxide ring
Using H+/H2O:
anti stereochemistry
Water attacks at the more substituted carbon

20. Reactions of Ethers Using H+/ROH: anti stereochemistry
ROH attacks at the more substituted carbon

21. Reactions of Ethers Base-Catalyzed Ring Opening of Epoxides:
SN2 attack of OH- or RO- on an epoxide ring
Anti stereochemistry
OH- and RO- attack at the least hindered (least substituted) carbon in the epoxide ring

22. Reactions of Ethers
Examples:

23. Reactions of Ethers
Reactions of Epoxides with Grignard and Organolithium Reagents
Attack of RMgX or RLi on the least hindered carbon in the epoxide ring forming an alcohol

24. Reactions of Ethers
Example:

25. Ethers
Examples: Predict the product of each of the following reactions.

26. Ethers
Examples:

27. Ethers
Example: How would you prepare the following compounds from the reactant given?