gcsescience.com                                       22                                       gcsescience.com

Products from Oil

What is an Isomer?

Isomers are compounds which have
the same molecular formula
but a different structural formula.

What is a Structural Formula?
The structural formula (also called the displayed formula)
shows how the atoms are joined together in the molecule.

Isomers of hydrocarbons have the same number
of carbon and hydrogen atoms
but the carbon atoms are joined to each other in
different ways. Simply changing the shape of
the molecule does not make it a different isomer.

The isomers of butane are shown on the next page.
Different isomers are different molecular compounds.
They will have different physical properties
(for example different boiling points).

The more carbon atoms a compound has,
the greater the number of isomers there can be.
Propane (3 carbon atoms) has 0 isomers.
Butane (4 carbon atoms) has 2 isomers.
Pentane (5 carbon atoms) has 3 isomers.
Hexane (6 carbon atoms) has 5 isomers.
Heptane (7 carbon atoms) has 9 isomers.
Octane (8 carbon atoms) has 15 isomers.

There are also isomers of alkenes and alcohols.

back        Links        Hydrocarbons        Revision Questions        next

gcsescience.com     The Periodic Table     Index     Hydrocarbons Quiz     gcsescience.com

Home      GCSE Chemistry      GCSE Physics

Copyright © 2015 gcsescience.com. All Rights Reserved.