Figure: 25-06
	Title:
	Hydrocarbon isomers.
	Caption:
	There are two structural isomers having the formula C4H10: butane and isobutane.  For the formula C5H12, there are three structural isomers; pentane, isopentane, and neopentane.  In general, the number of structural isomers increases as the number of carbons in the hydrocarbon increases.