1. Alkanes
Lecture 3

2. Outline Nomenclature, classification and isomerism
Methods of preparation
Chemical properties

3. CnH2n+2 Classification Hydrocarbons: Hydrocarbons: aliphatic saturated
alkanes
cycloalkanes
alkenes
cycloalkenes
alkynes
dienes
aromatic (arenes)
Hydrocarbons:
saturated
alkanes
cycloalkanes
unsaturated
alkenes
cycloalkenes
alkynes
dienes
arenes
Hydrocarbons:
cyclic
acyclic
CnH2n+2

4. Isomerism
Alkanes:
normal
(linear)
branched

5. Preparation of alkanes

6. Preparation of alkanes
C1 – C4
gas
200C
C5 – C9
raw material for organic syntheses
700C
C5 – C10
gasoline
1200C
C10 – C16
kerosene
1700C
C14 – C20
diesel fuel
2700C
C20 – C50
oils and waxes
C20 - C70
fuel
6000C >C70
tar

7. Preparation of alkanes
1. Wurtz reaction

8. Preparation of alkanes
2. Kolbe reaction
Mechanism:
1) oxidation of carboxylate ion on the anode
cathode process:
2) decarboxylation
3) recombination

9. Preparation of alkanes
3. Reaction of dialkylcuprates with alkyl halides
4. Hydrogenation of alkenes

10. Preparation of alkanes
5. Industrial methods
5.1 Coal liquefaction
5.2 From syngas (Fischer–Tropsch process)
water-gas shift:
steam reforming:

11. Chemical properties of alkanes
1. Radical reactions
1.1 Chlorination – a photochemical reaction
1) chain initiation
2) chain propagation
3) chain termination

12. Chemical properties of alkanes
1.1 Chlorination – a photochemical reaction
relative activity of secondary C-H
relative activity of primary C-H
57 / 2
43 / 6 4 1 =

13. Chemical properties of alkanes
1.2 Nitration – Konovalov reaction
1.3 Sulfochlorination reaction

14. Chemical properties of alkanes
2. Oxidation of alkanes
complete oxidation:
CH4 + 2O2 = CO2 + 2H2O
incomplete oxidation:
2CH4 + 3O2 = 2CO + 4H2O
CH4 + O2 = C + 2H2O
octane rating 100
octane rating 0