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Link to Isomerism Front Page

Structural Or Constitutional Isomers


 

Structural Isomers are molecules which have the same molecular formula but have different connectivities (The Order They Are Put Together). Alkanes can be very simple examples of this.

With the structural formula C4H10 there are two different isomers possible.

Straight Chain Alkane - click for 3D molfile Branched Chain Alkane - click for 3D molfile
 


As the number of Carbons in an alkane increases, the number of structural isomers also increases. This happens quite dramatically, as is shown by the following table.

 

 

Number of Isomers of Alkanes

Number of C Atoms Possible Isomers
1-3 1
4 2
5 3
6 5
7 9
8 18
9 35
10 75
15 4,347
20 366,319

 


 

Another simple example of Structural Isomerism is that between Alcohols and Ethers.
The molecular formula of both Ethanol (An Alcohol) and Methoxymethane (An Ether) is C2H6O.


 

Alkanes

Alkanes are the simplest class of organic compounds. They contain only tetravalent (making 4 covalent bonds) Carbon atoms and Hydrogen. Butane and Methylpropane are two examples which can be found on this page. As you can find on the other pages of this site they can only be involved in structural isomerism.