In chemistry, saturation (from the Latin word saturare, meaning 'to fill') has diverse meanings, all based on the idea of reaching a maximum capacity.
In organic chemistry, a saturated compound is a hydrocarbon which has no double or triple bonds. For example, consider three similar organic compounds that are progressively less saturated: ethane, ethylene, and acetylene (ethyne). Ethane, a completely saturated compound, has only single bonds between its hydrogen and carbon atoms (C2H6). Ethylene, an unsaturated compound of ethane, has a carbon double bond, having lost two hydrogen single bonds (C2H4). Finally acetylene, the completely unsaturated compound of ethane, has a carbon triple bond, having lost an additional pair of hydrogen single bonds (C2H2).
The concept of saturation can be described using various naming systems, formulas, and analytical tests. For instance, IUPAC nomenclature is a system of naming conventions used to describe the type and location of unsaturation within organic compounds. The "degree of unsaturation" is a formula used to summarize and diagram the amount of hydrogen that a compound can bind. Unsaturation can be determined by NMR, mass spectrometry and IR spectroscopy, or by determining a compound's bromine number.