1. Hydrocarbons

2. Aliphatic hydrocarbons
 Aliphatic
hydrocarbons are hydrocarbons
that consist of straight or branched chains
of carbon atoms, or rings of carbon atoms
other than those containing a special ring
called a benzene ring

3. Pentane – a straight chain
aliphatic hydrocarbon

4. A branched chain
hydrocarbon

5. Cyclohexane – a cyclic
aliphatic hydrocarbon

6. Homologous series
A
homologous series is a family of organic
compounds with the same general
formula, similar chemical properties, and
successive members differing by CH2
 Alkanes,
alkenes and alkynes are three
different homologous series of aliphatic
hydrocarbons

7. Alkanes
 Alkanes
are a homologous series of
hydrocarbons with the general formula
CnH2n+2
 They
are named systematically, with a
prefix indicating the number of carbon
atoms per molecule, and the ending
“ane”

8. Alkanes
 Methane
 Ethane
C2H6
 Propane
 Butane
CH4
C 3 H8
C4H10
 Pentane
 Hexane
 Heptane
 Octane
C5H12
C6H14
C7H16
C8H18

9. Alkanes
 Alkane
molecules
are tetrahedral,
e.g. propane

10. Structural formulas
 The
structural formula of an alkane
indicates the way atoms in a molecule of
the alkane are bonded together
 The following slides show the structural
formulas of some of the alkanes

11. Methane

12. Ethane

13. Propane

14. Butane

15. Pentane

16. Structural isomers



Structural isomers are compounds that have
the same molecular formula but different
structural formulas
Butane (C4H10)is the simplest alkane which has
structural isomers, called butane and 2methylpropane respectively
The name 2-methylpropane indicates that
there is a methyl (CH3) group attached
instead of one of the hydrogen atoms to the
second carbon in propane

17. Isomers of butane

18. An isomer of octane (C8H18)

2,2,4-trimethylpentane
is so called because
there are two methyl
groups attached (in
place of hydrogen
atoms) to the second
carbon atom and one
(in place of another
hydrogen atom) to the
fourth carbon atom in
a pentane molecule

19. Physical properties of alkanes
 Physical
state: The first four alkanes are
gases, while pentane and higher alkanes
are liquids
 Insoluble in water
 Soluble in non-polar solvents such as
cyclohexane

20. Alkenes
 Alkenes
are a homologous series of
hydrocarbons with the general formula
CnH2n
 They
are named systematically, with a
prefix indicating the number of carbon
atoms per molecule, and the ending
“ene”

21. Alkenes
 Ethene
C 2 H4
 Propene
C3H6
 But-1-ene
C4H8
 But-2-ene
C4H8

22. Ethene

23. Propene

24. But-1-ene

25. But-2-ene

26. Physical properties of alkenes
 Physical
state: Gases
 Insoluble
 Soluble
in water
in non-polar solvents such as
cyclohexane

27. Alkynes
 Alkynes
are a
homologous series
of hydrocarbons
with the general
formula CnH2n-2
 Ethyne
(C2H2) is the
first member of the
series

28. Physical properties of ethyne
 Physical
state: Gas
 Insoluble in water
 Soluble in non-polar solvents such as
cyclohexane