Let's assume that we want to find the structure of an unknown hydrocarbon. A molecular weight determination on the unknown yields a value of 82, which corresponds to a molecular formula of (CH). Since the saturated (C) alkene (hexane) has the formula (CH), the unknown compound has two fewer pairs of hydrogens (H14-H10=H4=2H), and its degree of unsaturation is two. The unknown therefore contains two double bonds, one ring and one double bond, two rings, or one triple bond. There's still a long way to go to establish structure but the simple calculation has told us a lot about the molecule.