Alcohols are compounds containing a hydroxyl (-OH) group. They are named based on the carbon chain and position of the hydroxyl group. Alcohols can be produced through fermentation of sugars by yeast or through hydration of alkenes with steam. They have low boiling points, are colorless and volatile. Alcohols can undergo combustion, oxidation, and dehydration reactions. Ethanol is used as a fuel and solvent, while alcohols in general have industrial and medical uses.

1.  Alcohols are compounds in which one or more
hydrogen atoms in an alkane have been replaced by an
-OH group
 General Formula:
 Functional Group:
 Naming of alcohol:
CnH2n+1OH
Hydroxyl
Number of
Carbon
1 2 3 4 5 6
Formula CH3OH C2H5OH C3H7OH C4H9OH C5H11OH C6H13OH
Name Methanol Ethanol
Propanol /
Propan-l-ol
Butanol /
Butan-l-ol
Pentanol /
Pentan-l-ol
Hexanol /
Hexan-l-ol
n = 1, 2, 3, ...
Alcohol

2. Naming alcohol
Example:
Longest chain: 3 carbon
(propanol)
Position of hydroxyl group: 2
Alkyl: -
Longest chain: 5 carbon
(pentanol)
Position of hydroxyl group: 1
Alkyl: -
Propan-2-ol
Pentan-1-ol

3. Longest chain: 3 carbon (propanol)
Position of hydroxyl group: 2
Alkyl: Methyl at 2nd carbon
Longest chain: 4 carbon (butanol)
Position of hydroxyl group: 1
Alkyl: Methyl at 3rd carbon
Longest chain: 3 carbon (propanol)
Position of hydroxyl group: 1
Alkyl: 2 methyls, both at 2nd carbon
2-methylpropan-2-ol
3-methylbutan-1-ol 2,2-dimethylpropan-1-ol

4. Isomerism of alcohol is because of:
• the position of hydroxyl group
• the presence of branch (alkyl group) in the molecule
Example: Isomers of propanol
Isomerism of Alcohol

5. Isomers of butanolExample:

6. a. Making ethanol by Fermentation
C6H12O6 → 2CH3CH2OH + 2CO2
Glucose Ethanol
Temperature : 18-20 °C
Catalyst : Zymase from yeast
Other condition : absence of oxygen
 From sugar & starches
 Yeast added
 Left in warm place (absence of oxygen) - anaerobic
Industrial Production of Ethanol

7. b. Making ethanol by hydration
C₂H₄ + H2O → C2H5OH
Ethene Steam Ethanol
 From petroleum fractions
Temperature : 300 °C
Pressure : 60 atm
Catalyst : phosphoric acid

8. Physical
properties
of alcohol
Boiling point
- Low boiling
point compare
to water
Odour
- Very sharp
smell
Colour
- Colourless
liquid at room
temperatureSolubility
- Simple alcohol are
very soluble in water
- Because has –OH
group
State
- C1 to C11 are
liquid at room
temperature
Highly volatile
- easily change
into gas

9. a. Combustion
 Complete combustion: produce CO2 + H2O
 Ethanol burns with a non-smoky blue flame
 Combustion of ethanol releases large
amount of heat.
 Ethanol suitable as a fuel
C2H5OH + 3O2 → 2CO2 + 3H2O
Chemical Properties of Alcohols

10. b. Oxidation
 React with the oxidation agent:
1. acidified potassium manganate(VII),
KMnO4 (purple → colourless)
2. acidified potassium dichromate(VI),
K2Cr2O7 (orange → green)
C2H5OH+ 2[O] → CH3COOH + H2O
Ethanol Ethanol acid

11. Alcohols can be
oxidised to produce
carboxylic acid
when react with
oxidising agents

12. c. Dehydration
 Removal of water molecule from alcohol
molecule
 Method:
1. Heated under reflux at 180 °C with excess
concentrated H2SO4 or
2. Pass over a heated catalyst
(porcelain chips, porous pot, Al2O3)
C2H5OH → C2H4 + H2O
Ethanol Ethene

13. Dehydration of Alcohols using
Aluminium Oxide as Catalyst
Catalyst: Aluminium oxide/ Porcelain chips

14. Dehydration of alcohols
using an acid catalyst
Catalyst: Sulphuric acid or Phosphoric acid
Temperature: 180°C

15. As beverage
• Alcohols can be used as a
beverage (ethanol only)
As fuel
• Some alcohol, mainly ethanol and
methanol, can be used as an
alcohol fuel.
• A mixture of petrol with 10 - 20%
ethanol (gasohol)
• Methanol (as a fuel for racing cars)
Use of Alcohol

16. As solvent
• Ethanol can be used as
solvent in perfumes,
cosmetics thinners for
lacquers, vernishers and
vegetable essences such as
vanilla.
As antiseptic
• Ethanol can be used as an
antiseptic to disinfect the
skin before injection are
given, often along with
iodine.

17. As source of medical
products
• Ethanol as a solvent in the
preparation of cough syrups
• Propan-2-ol as a rubbing
alcohol (bring down high fever)
As source of chemicals
• As a raw materials in the
manufacture of polymers,
fibers, explosives and plastics
• Ethanol  ethanoic acid
(vinegar)