HOMOLOGOUS SERIES
Joshua Baldwin
Definition
A Homologous Series is a group of organic
compounds that are like each other but differ
because of the addition of some extra atoms or
bonds (called a functional group).
Each homologous series has particular chemical
properties, that differentiate it from other series.
Properties
For example, the alkanes as a homologous series are
generally unreactive except for combustion reactions.
The alkanes, which have a C=C bond, are similar to
alkalines except that they are more reactive, because
the double bond can break open and join with other
atoms.
General Formulae
TENS, OR EVEN HUNDREDS, OF
DIFFERENT COMPOUNDS CAN
BELONG TO THE SAME
HOMOLOGOUS SERIES. TO HELP
CLARIFY AND IDENTIFY
COMPOUNDS IN A SERIES,
SCIENTISTS CAN USE A GENERAL
FORMULA TO CHARACTERIZE A
SERIES.
FOR EXAMPLE, ALKANES HAVE
THE GENERAL FORMULA:
C N H 2 N +2
WHERE N IS THE NUMBER OF
CARBON ATOMS IN THE
MOLECULE.
THIS RULE CAN BE USED FOR ALL
ALKANES WITH A STRAIGHT
CHAIN STRUCTURE.
This table shows the general formulae for the homologous series that you need to
know.
What are
homologues?
Homologues are the separate chemicals that
are a part of the series. They…
•
Contain similar functional groups
•
Share the same general formula
•
Have similar properties
•
Can be prepared by similar methods
(usually)
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