Chain isomerism

These isomers arise because of the possibility of branching in carbon chains. For example, there are two isomers of butane, C₄H₁₀. In one of them, the carbon atoms lie in a "straight chain" whereas in the other the chain is branched.

Be careful not to draw "false" isomers which are just twisted versions of the original molecule. For example, this structure is just the straight chain version of butane rotated about the central carbon-carbon bond.

You could easily see this with a model. This is the example we've already used at the top of this page.