Question

What are the isomers of butane?

Answer 1

Butane, or `C_4H_10`, has two structural (also called constitutional) isomers called normal butane, or unbranched butane, and isobutane, or i-butane. According to IUPAC nomenclature, these isomers are called simply butane and 2-methylpropane.

As you know, isomers are molecules that have the same molecular formula but different chemical structures. In the case of butane, its two isomers will have these structural formulas

Notice that isobutane has a propane parent chain with a methyl group - `CH_3` attached to the second carbon of the chain - that is why its IUPAC name is 2-methylpropane.