chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, a saturated compound is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

(or ion) that resists the addition reactions, such as

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...

oxidative addition Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidat ...

, and binding of a

Lewis base A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

. The term is used in many contexts and for many classes of chemical compounds. Overall, saturated compounds are less reactive than unsaturated compounds. Saturation is derived from the Latin word ''saturare'', meaning 'to fill'.

Organic chemistry

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 bonds between carbon atoms. An important class of saturated compounds are the

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

s. Many saturated compounds have functional groups, e.g.,

alcohols In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

Unsaturated organic compounds

The concept of saturation can be described using various naming systems,

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

s, and analytical tests. For instance,

IUPAC nomenclature A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC). The ...

is a system of naming conventions used to describe the type and location of unsaturation within organic compounds. The "

degree of unsaturation In the analysis of the molecular formula of organic molecules, the degree of unsaturation (also known as the index of hydrogen deficiency (IHD), double bond equivalents, or unsaturation index) is a calculation that determines the total number of r ...

" is a

used to summarize and diagram the amount of hydrogen that a compound can bind. Unsaturation can be determined by

NMR Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with ...

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

and

IR spectroscopy Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functiona ...

, or by determining a compound's

bromine number In chemistry, the bromine number is the amount of bromine () in grams absorbed by of a sample. The number indicates the degree of unsaturation. The bromine number is useful as a measure of aliphatic unsaturation in gasoline samples. The Calif ...

iodine number Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

Fatty acids

The terms saturated vs unsaturated are often applied to the

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

constituents of

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

s. The triglycerides (fats) that comprise

tallow Tallow is a rendering (industrial), rendered form of beef or mutton fat, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain techn ...

are derived from the saturated stearic and monounsaturated

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega ...

s. Many

vegetable oil Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...

s contain fatty acids with one (''monounsaturated'') or more (''polyunsaturated'') double bonds in them.

Saturated and unsaturated compounds beyond organic chemistry

Organometallic chemistry

organometallic chemistry Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

, a coordinatively unsaturated complex has fewer than 18 valence electrons and thus is susceptible to

or coordination of an additional

ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...

. Unsaturation is characteristic of many

catalysts Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

. The opposite of coordinatively unsaturated is coordinatively saturated. Complexes that are coordinatively saturated rarely exhibit catalytic properties.

Surfaces

physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mecha ...

, when referring to surface processes, saturation denotes the degree at which a binding site is fully occupied. For example,

base saturation Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with o ...

refers to the fraction of exchangeable cations that are base cations.

References

{{DEFAULTSORT:Unsaturated Compound Organic chemistry Chemical nomenclature