1. Alcohols and ethers

2. R = alkyl group (substituted or unsubstituted)
Structure
R-OH alcohol
R = alkyl group (substituted or unsubstituted)

3. Sterols - the steroid ring system

4. Physical properties of alcohols
Alcohols are noticeably less volatile; their melting points are greater and they are more water soluble than the corresponding hydrocarbons having similar molecular weights.
These differences are due to the OH group which renders a certain polarity to the molecule. The result is an important intermolecular attraction:

5. Solubility of alcohols
Low molecular weight alcohols are water soluble:

6. Spectroscopic properties
IR:
Unassociated alcohols show a fairly sharp absorption near 3600 cm-1 due to O-H stretching. Associated alcohols (hydrogen bonded) show a broad absorption in the cm-1 range.

7. Fermentation Fermentation of sugar by yeast gives C2H5OH.
Methanol is added to denature it.

8. Azeotropic mixtures
The bp of ethanol is 78.3C whereas that of water is 100C (at least on Vancouver’s waterfront!). Can we separate a mixture by distillation?
No! An azeotropic mixture forms!
An azeotropic mixture is one whose liquid and vapor forms have identical compositions. The mixture cannot be separated by distillation.
eg C2H5OH (95%) and H2O (5%) - bp 78.13C
H2O (7.5%), C2H5OH (18.5%) and C6H6 (74%) - bp 64.9C

9. Oxymercuration

10. Hydroboration
syn
addition

11. Reactions of alcohols
The reactions of alcohols involve one of two processes:
breaking of the O-H bond
breaking of the C-O bond

12. Reactions involving O-H bond breaking
R-OH + M
RO- + M /2 H2

13. Reactions involving C-O bond breaking - dehydration

14. Reactions involving C-O bond breaking - dehydration
E1 mechanism

15. Reaction with hydrogen halides

16. Experimental facts 1. The reaction is acid catalyzed
2. Rearrangements are possible
3. Alcohol reactivity is 3o > 2o > 1o < CH3OH

17. The mechanism

18. Reaction of primary alcohols with HX
SN2
This reflects nucleophile strength in a protic solvent.

19. Reactions with phosphorus halides and with thionyl chloride
ROH + PX3
RX + H3PO3
Creates a good leaving group from 1o and 2o alcohols.

20. Tosylates

21. Why form tosylates?
Sulfonate ions are excellent leaving groups:

22. Ethers Structure: R-O-R, Ar-O-R, or Ar-O-Ar nomenclature
Name the two groups bonded to the oxygen and add the word ether.
CH3CH2OCH2CH3 - diethyl ether

23. Nomenclature of ethers
diphenyl ether
CH3OCH=CH2
methyl vinyl ether
isopropyl phenyl ether
3-methoxyhexane
CH3CH2CH2CHCH2CH3 |
OCH3

24. Nomenclature of cyclic ethers
Use the prefix oxa- to indicate that an O replaces a CH2 in the ring.
oxacyclopropane
ethylene oxide
oxacyclopentane
tetrahydrofuran
1,4-dioxacyclohexane
1,4-dioxane

25. Williamson synthesis
A primary halide is necessary to ensure an SN2 reaction and not an E2 elimination.

26. Reaction of ethers
What is the mechanism?

27. Epoxides
syn addition

28. Mechanism

29. Reactions
What is the mechanism?