1. Mdm Rohazita Bahari ERT 102 Organic Chemistry 2017 2018
Alcohols & Ethers
Mdm Rohazita Bahari
ERT 102
Organic Chemistry

2. Alcohols & Ethers
Alcohols and ethers are organic derivatives of water where one or both H atoms are replaced by R groups.
H-O-H  R-O-H  R-O-R’
Water
Alcohol
Ether

3. Alcohols
Functional group is -OH, the hydroxyl group, bonded to a tetrahedral carbon
Nomenclature Rules
Same as for Alkenes and Alkynes except you only drop the -e, and add -ol!
propane propanol

4. Nomenclature of Alcohols
1) Select the longest chain that contains the carbon bonded to the -OH group, and number the chain to give the carbon bonded to the -OH group the lowest number
The -OH group takes precedence over alkyl groups, double bonds, triple bonds, and halogens!!!

5. Nomenclature of Alcohols
2) Change the suffix by dropping the -e, and adding -ol. Use the number to show location. In cycloalkanes, start numbering from the carbon bonded to the -OH.
3) Name and number substituents and list them in alphabetical order.

6. Naming Alcohols 1. The parent chain must contain the –OH group. Change
parent ending to “-ol”.
2. Give the –OH the lowest possible number.
6,6-dimethyl-3-heptanol

7. Alcohol Nomenclature 1º methanol methyl alcohol ethanol ethyl alcohol3º 2º
2-propanol
isopropyl alcohol
2-methyl-2-propanol
tert-butyl alcohol

8. OH > C=C > R, X
4-methyl-2-pentanol
4-chloro-2-methyl-2-pentanol
2,6-dichloro-4-methyl-4-octanol

9. OH > C=C > R, X
4-penten-2-ol
5-chloro-3-hexen-2-ol
3-chloro-2-ethyl-2-buten-1-ol

10. Naming Alcohols
3. When the –OH group is attached to a ring, it is assumed
to be at carbon #1.
2-methylcyclopentanol
(NOT 2-methyl-1-cyclopentanol)

11. Classification
We classify alcohols as 1o, 2o, and 3o, depending on the classification of the carbon they are bonded to.

12. Multiple -OH’s present
Molecules with 2 -OH’s are named as diols
Molecules with 3 -OH’s are named as triols
(Note: you do not drop the -e when using diol, triol, etc)
Compounds with 2 -OH’s are refered to as glycols

13. Physical Properties of Alcohols
The most important physical property is their polarity
Both the C-O bond and the O-H bond are polar covalent bonds
Thus alcohols are polar molecules
They also have the ability to hydrogen bond.
These factors lead to higher B.P’s, M.P’s. etc

14. Physical Properties of Alcohols
Because of increase London forces (van der Waals forces) between larger molecules, the B.P. of all types of compounds, including alcohols, increase as molecular weight increases
Alcohols are much more soluble in H2O due to their H-bonding capacity.
As MW increases, the water solubility of alcohols decreases
This is because the hydrocarbon portion of the molecule dominates.

15. Reactions of Alcohols Acidity of Alcohols
-Alcohols are considerably weaker acids than carboxylic acids, but can lose their hydrogen in an acid-base reaction.

16. Methanol
Methanol was once prepared by the destructive distillation of wood.
Wood alcohol.
Toxic, causes blindness in low doses (15 mL).
Routinely used as a solvent and starting material.
Methanol used by the chemical industry is prepared by the catalytic reduction of carbon monoxide.
CO H CH3OH
250°C
Cu/ZnO/Al2O3

17. Ethanol H2C=CH2 + H2O CH3CH2OH
Prepared by the fermentation of grains and sugars.
Grain alcohol.
Used in alcoholic beverages.
The largest single use of ethanol is as a motor fuel and fuel additive (replaces MTBE).
5 billion gallons are prepared (primarily from corn) annually in the U.S. for fuel uses.
Ethanol used by the chemical industry is prepared by the acid-catalyzed hydration of ethylene.
H2C=CH H2O CH3CH2OH
250°C
H3PO4

18. The Polar -OH Group
The physical properties of the alcohols are strongly influenced by the polar -OH group.
Electrostatic Potential Map
Negatively polarized oxygen
Methanol
Neutral methyl group
Positively polarized hydrogen

19. Boiling Points
The polar -OH group allows hydrogen bonding to take place in alcohols. These strong intermolecular forces result in higher than expected boiling points. - +
CH3CH2CH2OH
CH3CH2Cl
CH3CH2CH2CH3
Compound
MW (g/mol)
BP (°C) 58
-0.5 65
12.5 60 97

20. Ethers
Structure- functional group is a Oxygen bonded to 2 carbons
Simplest ether is dimethyl ether

21. Nomenclature of Ethers
The common naming system is used for simple ethers:
List the alkyl groups bonded to the oxygen in alphabetical order, followed by the work “ether”.

22. Ether Nomenclature diethyl ether ethyl methyl ether
cyclohexyl methyl ether
cyclooctyl ethyl ether

23. Crown Ethers
Large rings consisting repeating (-OCH2CH2-) or similar units
Named as x-crown-y
x is the total number of atoms in the ring
y is the number of oxygen atoms
18-crown-6 ether: 18-membered ring containing 6 oxygens atoms
Central cavity is electronegative and attracts cations

24. 18-Crown-6

25. Uses of Crown Ethers
Complexes between crown ethers and ionic salts are soluble in nonpolar organic solvents
Creates reagents that are free of water that have useful properties
Inorganic salts dissolve in organic solvents leaving the anion unassociated, enhancing reactivity

26. Physical Properties of Ethers
Ethers are polar compounds
The oxygen has a partial minus charge, the carbons bonded to the oxygen have a partial positive charge
Ether have very weak intermolecular forces which results in low boiling points

27. Electrostatic Potential Map Negatively polarized oxygen
The Ethers
Ethers lack the polar -OH group and therefore do not have hydrogen bonding.
Electrostatic Potential Map
Diethyl ether
Negatively polarized oxygen
Neutral ethyl group
Neutral ethyl group

28. Reactions of Ethers
Like alkanes, they are resistant to most chemical reactions
Therefore, they are ideal to use as solvents

29. Diethyl Ether 2 CH3CH2OH CH3CH2OCH2CH3 + H2O
Was once widely used as an anesthetic.
Highly flammable.
Presently used as a solvent.
Prepared by the sulfuric acid-catalyzed dehydration of ethanol.
2 CH3CH2OH CH3CH2OCH2CH H2O
H2SO4

30. Boiling Points
Ethers have weak intermolecular forces, which results in low boiling points. Low molecular weight ethers are highly volatile.
CH3CH2CH2CH2OH
CH3OCH3
Compound
MW (g/mol)
BP (°C)
CH3CH2OH
CH3CH2OCH2CH3 46
78.5 46
-25 74
117.2 74
34.5

31. Alcohols & Ethers
Alcohols and ethers have very different chemical and physical properties. This is due to the polar -OH group that’s present in alcohols but absent in ethers.
ROR’
ROH
Compound BP
Polarity
Hydrogen-Bonding?
Reactive?
Uses
starting materials
polar
yes
high
yes
non-polar no
low no
solvents

32. Reactions: OXIDATION & REDUCTION
ALCOHOL
Reactions:
OXIDATION & REDUCTION

33. Basic need to know Type of alcohol What is carbonyl group Oxidation
Reduction

34. Type of alcohol
PRIMARY ALCOHOL
SECONDARY ALCOHOL
TERTIARY ALCOHOL

35. Carbonyl group Aldehyde Ketone Carboxylic Acid Ester
What is carbonyl group?
Aldehyde
Ketone
Carboxylic Acid
Ester

36. oxidation
reduction
Is the loss of electrons (e-) and loss of hydrogen atom
Up charge
Is the gain of electrons (e-) and gain of hydrogen atom
Reduce charge

37. A reaction involving electron transfer
Called it as redox reaction
example:
Fe + CuSO FeSO4 + Cu

38. Oxidation-Reduction
An oxidation reduction reaction or a redox reaction is one which electron transfer occurs
In organic chemistry this tends to have a significance more on par of oxygen content
Oxidation reactions as ones in which carbon gains bonds to oxygen
Reduction reactions as ones in which carbon atoms lose bonds to oxygen.

39. oxidation Just to take a look at oxidations.
We can oxidize primary or secondary alcohols
A tertiary alcohol cannot be oxidized because that carbon cannot already has three bonds to other carbons.
So, there are not any bonds that can be replaced to give carbon more bonds to oxygen.
It is going to be possible to gain more oxygen here

40. oxidation
For oxidation, we usually used PCC, Pyridinium chlorochromate to get aldehyde for primary alcohols & ketone for secondary alcohols
It is a reagent in organic synthesis used primary for oxidation of alcohols.
We use Jones oxidation (CrO3 + H2SO4) to get carbocyclic acid for primary alcohols and ketones for secondary alcohols.

41. reduction Carbonyl compound to alcohol
Use different reducing agents and again these have different strengths.
Sodium borohydrate (NaBH4) and Lithium aluminum hydride (LiAlH4)
LiAlH4 more stronger than NaBH4.
NaBH4 only reduce aldehyde and ketones
LiAlH4 can reduce aldehyde, ketones including carboxylic acid and ester.

42. Oxidation and Reduction
Carboxylic Acid
REDUCTION
Aldehyde / Ketone
Alcohol
Alkane
Oxidation: Increase C-O bonds Reduction: Increase C-H bonds

43. Common Reducing Agents
Sodium borohydride (NaBH4) is a mild reducing agent.
aldehyde
1º alcohol
ketone
2º alcohol

44. Common Reducing Agents
Lithium aluminum hydride (LiAlH4) is a strong reducing agent.
carboxylic acid
1º alcohol

45. Predict the Products

46. Common Oxidizing Agents
Pyridinium chlorochromate (PCC) (C5H6NCrO3Cl) is a mild oxidizing agent.
1º alcohol
aldehyde
2º alcohol
ketone

47. Common Oxidizing Agents
Chromium trioxide (CrO3) and sodium dichromate (Na2Cr2O7) are strong oxidizing agents.
1º alcohol
carboxylic acid
2º alcohol
ketone

48. Predict the Products

49. The Williamson Ether Synthesis
Is the reaction that converts alcohol (R-OH) into ethers (R-O-R).
The 1st step in this reaction is forming the conjugate base of the alcohol (called an alcoxide) by reacting the alcohol with sodium metal.
This reaction forms hydrogen gas (H2) as a bioproduct.

50. The Williamson Ether Synthesis R can be 1º, 2º, 3º, or cycloalkyl.
2 ROH M  2 ROM H2
alcohol
M = Na, K
RO R’X  ROR’ X-
SN2
alkoxide
alkyl halide
ether
R can be 1º, 2º, 3º, or cycloalkyl.
R’ should be methyl or 1º.

51. Synthesis of Diethyl Ether via the Williamson Synthesis
Diethyl ether is a symmetrical ether.
2 CH3CH2OH + 2 Na  2 CH3CH2ONa + H2
ethanol
sodium ethoxide
CH3CH2O- + CH3CH2I  CH3CH2OCH2CH3 + I-
SN2
ethoxide ion
ethyl iodide
diethyl ether

52. Synthesis of tert-Butyl Methyl Ether via the Williamson Synthesis
tert-Butyl methyl ether is an asymmetrical ether.
SN2 +
This is the better route
nucleophile
tert-butyl methyl ether E2 + +
base
2-methylpropene