Coordinatively unsaturated

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 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 ethyne, 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.

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