Saturation and Unsaturation
The distinction between compounds containing only single bonds and those containing multiple bonds or rings.
Formula / equation
DoU = (2C + 2 + N − H − X)/2
Unit
Dimensionless
In depth
The degree of unsaturation calculated from a molecular formula counts the total number of rings and pi bonds, which is often the first structural clue from a mass spectrum. Unsaturated compounds add reagents across their multiple bonds, decolourising bromine water.
Examples in the real world
Benzene has four degrees of unsaturation — one ring and three pi bonds; hexane has none.