Isomers

Isomers are molecules that have the same molecular formula, but different structures. For example, butene can exist as the two isomers:

But-1-ene:

but-1-ene

But-2-ene:

but-2-end

 

These isomers have the same molecular formula, C4H8

Symmetry

When identifying isomers, be careful to keep in mind the symmetry of the molecule. Although shown differently, the two molecules below are both 2-methylbutane as they have a methyl group on the second carbon on the 4-carbon chain.

2-methylbutane1 2-methylbutane2