1. (1.2) Hydrocarbons
Alkanes

2. Alkanes
bonds are still relatively weak yet a single bond is harder to break than a multiple bond
are non-polar and have weak intermolecular force, therefore relatively low boiling points
boiling point increases with an increase in number of atoms (increasing intermolecular force)

3. Alkanes
# C atoms
BP (0 C)
1-5
<30
5-16
40-275
16-22
>250
>18
>400
>26
>500
Because of the variety in structure and length, its hard to classify alkanes in certain boiling point range.

4. Naming Alkanes Use the IUPAC method Based on number of carbon atoms
Use “-ane” as a suffix
Ex: methane
ethane
# C atoms
Root 1
Meth 2
Eth 3
Prop 4
But 5
Pent 6
Hex 7
Hept 8
Oct 9
Non 10
Dec

5. Naming Alkanes Use general formula for alkanes
CnH2n+2 where n= # C atoms
ex.
Propane (C3H8)
Heptane (7 C atoms)
(C7H16)

6. Alkanes As a group of compounds alkanes form a homologous series.
Each molecule differs from the next by the structural unit CH2
ex. ethane, propane, butane

7. Straight Chained Alkanes
Count the number of carbons present in the chain.
This determines the “root”
Ex.Name the following compounds
a) CH3(CH2)7CH3 b) c)
Ans: nonane, methane, ethane

8. Straight Chained Alkanes
Ex. Draw the following
a) Propane (complete structural diagram)
b) Decane (condensed structural diagram)
c) Pentane (line structural diagram)

9. Branched Chained Alkanes – Step 1
Find the longest continuous chain (parent chain or backbone)
Ex: 5 = pent (root)
since there are only single bonds use the suffix - ane

10. Branched Chained Alkanes
Ex. What is the longest carbon chain in the following?

11. Branched Chained Alkanes – Step 2
Identify any branches.
Number the main chain from the end that gives the lowest number for 1st location at which branch occurs. 11 21 31 41 51

12. Branched Chained Alkanes – Step 3
Alkyl group: hydrocarbon group from an alkane by removing a hydrogen
Name branch using root name (table 2 –p12) and change the ending to –yl
Ex. –CH3
methyl

13. Branched Chained Alkanes – Step 4
Indicate the point of attachment of the alkyl group to the hydrocarbon backbone.
For this we number the C’s in the parent chain.
Numbering system must give the lowest possible combinations.
Ex.2-methylpentane

14. Branched Chained Alkanes
Ex. Draw the following
3-ethylhexane

15. Branched Chained Alkanes
We separate….
numbers from numbers by a comma (,)
and
numbers from letters with a hyphen (-)
Spelling Counts!

16. Branched Chained Alkanes
When multiple branches of the same type are present:
Use the suffix di, tri, tetra etc. before the alkyl group
Ex.
a) 2,3-dimethylhexane
b) 2,3,3-trimethylpentane

17. Branched Chained Alkanes
When multiple branches of the different type are present:
Name the alkyl groups, with number indicating position on parent chain, in alphabetical order.
Note: Some textbooks may be different.
Ex. a) 3-ethyl-5-methylheptane
b) 4-ethyl-2,3-dimethyloctane
Recall: alphabetical order for alkyl groups, excluding prefix

18. Branched Chained Alkanes
Ex. Name the following:
CH3-CH-CH2-CH-CH2-CH-CH3
CH2CH3
CH3
CH2CH2CH3

19. Isomers
Isomers have the same molecular formula but different structures.
They have different properties (ex. melting/boiling points, density, reactivity )

20. Isomers – Example 1 Butane – C4H10 IUPAC Name: butane 2-methylpropane
Common Name: n-butane i-butane
(normal butane) (isobutane)

21. Isomers – Example 2 Pentane - C5H12
Draw all of the ways this compound could be structured. Then name the isomers!
(Hint – there are 3 isomers)
Ans:
pentane, 2-methylbutane, 2,2-dimethylpropane

22. Isomers of Alkyl Groups
When we consider potential attachment points, there are 2 propyl isomers (-C3H7):
p13
Figure 4
Note: The coloured bond indicates where the group is attached to the larger molecule

23. Isomers of Alkyl Groups
There are 4 butyl isomers (-C4H9):
p13
Figure 4