Asaturated compound is achemical compound (or ion) that resistsaddition reactions, such ashydrogenation,oxidative addition, and binding of aLewis base. The term is used in many contexts and classes of chemical compounds. Overall, saturated compounds are less reactive than unsaturated compounds. Saturation is derived from the Latin wordsaturare, meaning 'to fill'.[1]
Generally distinct types of unsaturated organic compounds are recognized. For hydrocarbons:
For organic compounds containing heteroatoms (other than C and H), the list of unsaturated groups is long but some common types are:
| Saturated compounds | ||
|---|---|---|
 |  |  |
| Unsaturated compounds | ||
|---|---|---|
 |  |  alpha-Linolenic acid, an unsaturated fatty acid |
Unsaturated compounds generally carry out typical addition reactions that are not possible with saturated compounds such as alkanes. A saturated organic compound has only single bond between carbon atoms. An important class of saturated compounds are thealkanes. Many saturated compounds have functional groups, e.g.,alcohols.
The concept of saturation can be described using various naming systems,formulas, andanalytical 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 aformula used to summarize and diagram the amount of hydrogen that a compound can bind. Unsaturation can be determined byNMR,mass spectrometry, andIR spectroscopy, or by determining a compound'sbromine number oriodine number.[2]
The terms saturated vs unsaturated are often applied to thefatty acid constituents offats. The triglycerides (fats) that comprisetallow are derived from the saturatedstearic and monounsaturatedoleic acids.[3] Manyvegetable oils contain fatty acids with one (monounsaturated) or more (polyunsaturated) double bonds in them.
Inorganometallic chemistry, a coordinatively unsaturated complex has fewer than18 valence electrons and thus is susceptible tooxidative addition or coordination of an additionalligand. Unsaturation is the characteristic of manycatalysts. The opposite of coordinatively unsaturated is coordinatively saturated. Complexes that are coordinatively saturated rarely exhibit catalytic properties.[4][5]
Inphysical chemistry, when referring to surface processes, saturation denotes the degree at which a binding site is fully occupied. For example,base saturation refers to the fraction ofexchangeable cations that are base cations.