1. Alcohols, Ethers, Thiols and Chirality
Chemistry 20
Chapters 5 & 6
Alcohols, Ethers, Thiols and Chirality

2. Alcohols Alcohols Contain a hydroxyl group (-OH).
Phenols Contain a benzene ring with a hydroxyl
group (-OH). OH

3. Naming Alcohols IUPAC name: We replace the -e in alkane name with -ol.
Common name: As simple alcohols using the name of the alkyl group followed by “alcohol”.
CH4 methane
CH3─OH methanol (methyl alcohol)
CH3─CH3 ethane
CH3─CH2─OH ethanol (ethyl alcohol)

4. Naming Alcohols Step 1 Step 2 Step 3 Step 4
Select the longest carbon chain
that contains the -OH group.
Step 2
Number from the end nearest -OH group.
Step 3
Change the ending of parent alkane from -e to -ol.
Use the number to show the location of -OH.
Step 4
Give the location and number of each substituent
(alphabetical order) as a prefix to the name of the
main chain.

5. Naming Alcohols CH3─CH2─CH2─OH 1-propanol OH │ CH3─CH─CH3 2-propanol
│ │
CH3─CH─CH2─CH2─CH─CH methyl-2-hexanol 3 2 1 3 2 1 6 5 4 3 2 1

6. Naming Alcohols OH │ CH3─CH─CH2─CH3 2-butanol CH3
CH3─CH─CH ─CH2─OH 3-chloro-2-methyl-1-butanol
CH3─C─CH2─OH ,2-dimethyl-1-propanol 1 2 3 4 Cl 4 3 2 1
CH3 3 2 1

7. Diols & Triols Diol: a compound containing two –OH (Hydroxyl groups).
Triol: a compound containing three –OH (Hydroxyl groups).
CH2 – CH2
CH3 – CH – CH2
CH2 – CH – CH2 OH OH OH OH OH OH OH
1,2-Ethanediol
(Ethylene glycol)
1,2-Propanediol
(Propylene glycol)
1,2,3-Propanetriol
(glycerol, glycerin)

8. Different types of Alcohols
Primary (1º) Secondary (2º ) Tertiary (3º)
H CH CH3
│ │ │
CH3─C─OH CH3─C─OH CH3─C─OH
H H CH3
1 C C C
attached attached attached
to C-OH to C-OH to C-OH

9. Phenol Phenol is the IUPAC name for benzene with a hydroxyl group. OH
Many are used as antiseptics and disinfectants.
Is a weak acid. OH
Phenol

10. Physical Properties of Alcohols
Alcohols are polar molecules (because of O-H and C-O).
Hydrogen bonding between alcohols molecules.
Have higher boiling points than Alkanes, Alkenes, and Alkynes.
Molecular weight ↑ : London dispersion forces ↑ : bp ↑
More soluble in water (Molecular weight ↑ : solubility ↓).
They are weak acids (weaker than Phenol).
polar
nonpolar OH

11. Chemical Properties of Alcohols
1. Acidity of Alcohols:
2. Acid-Catalyzed Dehydration:
H2SO4
CH3CH2OH
CH2 = CH2 + H2O
180°C
Dehydration
- C – C -
C = C + H20
Hydration H OH
3. Oxidation of Alcohols:

12. Acid-Catalyzed Dehydration
H2SO4 1°
CH3CH2OH
CH2 = CH2 + H2O
High T
180°C OH
H2SO4
CH3CHCH3
CH2 = CH - CH2 + H2O 2°
Moderate T
140°C OH
H2SO4 3°
CH3 C CH3
CH3 C = CH2 + H2O
Low T
50°C
CH3
CH3 1° 2° 3°
Ease of dehydration of alcohols

13. Acid-Catalyzed Dehydration
Alkene having the greater number of alkyl groups on the double bond
generally predominates.

14. Oxidation of 1° Alcohols
In the oxidation [O] of a primary alcohol 1, one H is
removed from the –OH group and another H from the C
bonded to the –OH.
primary alcohol aldehyde
OH O
│ ║
CH3─C─H CH3─C─H + H2O │ H
ethanol ethanal
(ethyl alcohol) (acetaldehyde)
[O]
K2Cr2O7
H2SO4

15. Oxidation of 2° Alcohols
The oxidation of 2 alcohols is similar to 1°, except that a
ketone is formed.
secondary alcohol ketone
OH O
│ ║
CH3─C─CH CH3─C─CH3 + H2O │ H
2-propanol propanone
[O]
K2Cr2O7
H2SO4

16. Oxidation of 3° Alcohols
Tertiary 3 alcohols cannot be oxidized.
Tertiary alcohol no reaction OH │
CH3─C─CH3 no product
CH no H on the C-OH to oxidize
2-methyl-2-propanol
[O]
K2Cr2O7
H2SO4

17. Oxidation of Alcohols in our body
In the body:
Enzymes in the liver oxidize ethanol.
Blood alcohol over 0.4% can be fatal.
O O
║ ║
CH3CH2OH CH3CH CH3COH CO2 + H2O + Energy
ethanol ethanal acetic acid
[O]
[O]
[O]

18. Ethers

19. Ethers An ether: Contains an -O- between two carbon atoms.
Is named from alkyl names of the attached groups
(in alphabetical order) followed by ether.
CH3─O─CH3 CH3─CH2─O─CH3
dimethyl ether ethyl methyl ether

20. Cyclic Ethers
One of the atoms in a ring is oxygen.

21. Physical Properties of Ethers
They are polar compounds (because of C-O).
Weak dipole-dipole interactions.
Low boiling points: Hydrocarbons < ethers < alcohols.
More soluble in water than other hydrocarbons
of similar molecular weight (H-bond with water). δ- δ+
C-O
(3.5 – 2.5 = 1) H δ+ O H δ-

22. Chemical Properties of Ethers
Ethers are resistant to chemical reactions (inert).
Oxidation
Reduction
Good solvent for organic reactions.

23. Thiols

24. Thiols An Thiol: Contains an –SH (sulfhydryl) group.
Is named by selecting the longest carbon chain that contain the -SH. We add -thiol to the name of the parent alkane.
Parent chain is numbered from the end nearest to
the -SH group.
CH3─S─H CH3─CH2─S─H
Methanethiol Ethanethiol

25. Naming Thiols Step 1 Step 2 Step 3 Step 4
Select the longest carbon chain
that contains the -SH group.
Step 2
Number from the end nearest -SH group.
Step 3
Add –thiol to the name of the parent alkane.
Use the number to show the location of -SH.
Step 4
Give the location and name of each substituent
(alphabetical order) as a prefix to the name of the
main chain.

26. 4-Methyl-1-pentanethiol
CH3
CH3CHCH2CH2CH2SH
4-Methyl-1-pentanethiol 5 4 3 2 1
CH3
CH3CHCH2SH
2-Methyl-1-propanethiol 3 2 1 Cl
CH3 SH
CH3-CH-CH2-CH-CH-CH3
5-Chloro-3-methyl-2-hexanethiol 6 5 4 3 2 1

27. Physical Properties of Thiols
They have unpleasant odors.
They are nonpolar compounds.
S-H (2.5 – 2.1 = 0.4) nonpolar covalent.
3. Low boiling points (London dispersion forces).
4. Almost insoluble in water.

28. Chemical Properties of Thiols
1. Thiols are weak acids (react with strong bases).
H2O
CH3CH2SH + NaOH CH3CH2S-Na+ + H2O
Sodium ethanethiolate
2. Oxidation to disulfides: -S-S- disulfide
Oxidation
2HOCH3CH2SH + O HOCH2CH2S-SCH2CH2OH
Reduction

29. Chirality

30. same
connectivity
Stereoisomers
Chiral
Enantiomers
Diastereomers
Constitutional Isomers
Cis-Trans
Isomers
with
stereocenters
without
Achiral
different

31. A

32. superposable mirror images
Achiral
superposable mirror images
2-propanol
This means that the original and its mirror image are the similar molecules.

33. nonsuperposable mirror images
Enantiomers (chiral)
nonsuperposable mirror images
2-butanol
They have different chemical and physical properties.

34. stereocenter A carbon with four different groups bonded to it.
It usually creates enantiomers.