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10.1 Homologous Series and Functional Groups
Date _____________________________
10.1.1 Describe the features of a homologous series
 Members of a homologous series have the same functional group and can be represented by
the same general formula.
 Successive members of the series have an additional CH2 group
 The members of a series show a gradual change in their physical properties, as the chain length
increases
 The members of a series have similar chemical properties due the presence of the same
functional group within a series
Example: The alkanes form a series of compounds all with the general formula
CnH2n+2
Straight Chain Alkanes – An Example of a Homologous Series
# Carbon
Name
Molecular
Formula
Structural
Formula
1
Methane
CH4
CH4
2
Ethane
C2H6
CH3CH3
3
Propane
C3H8
CH3CH2CH3
4
Butane
C4H10
CH3CH2CH2CH3
5
Pentane
C5H12
CH3CH2CH2CH2CH3
6
Hexane
C6H14
CH3(CH2)4CH3
7
Heptane
C7H16
CH3(CH2)5CH3
8
Octane
C8H18
CH3(CH2)6CH3
9
Nonane
C9H20
CH3(CH2)7CH3
10
Decane
C10H22
CH3(CH2)8CH3
10.1.2 Predict and explain the trends in the boiling points of members of a homologous series.
As we have already discussed, the boiling points of the alkanes increase gradually as the carbon chain
length increases. [You should be able to explain this in terms of increasing vanderWaal’s]
http://jchemed.chem.wisc.edu/
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Other homologous series are all characterized by the presence of a particular FUNCTIONAL GROUP.
Use your text to identify the general formula, functional group and an example of the following
homologous series.
NOTE: “-R” is sometimes used to denote a hydrocarbon chain in a general formula
Name of Functional
General Formula or
Example (Name and Structural Formula)
Group
Alkenes
Alcohols
Halogenoalkanes
Aldehydes
Ketones
Carboxylic Acids
Esters
READ Brown-Ford pages 185 to 188
READ Brown-ford pages 197 and 198 and SUMMARIZE these IDEAS FOR YOUR NOTES.
Try the animated tutorial mentioned on p. 197.
Complete your practice nomenclature sheets for alkanes, alkenes and alkynes