In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
, 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 catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...
,
oxidative addition, 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 wh ...
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 betwe ...
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).
Th ...
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
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 betwe ...
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 or
iodine number.
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, f ...
constituents of
fats. The triglycerides (fats) that comprise
tallow
Tallow is a 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 technical criteria, includ ...
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 o ...
s.
Many
vegetable oils contain fatty acids with one (''monounsaturated'') or more (''polyunsaturated'') double bonds in them.
Saturated and unsaturated compounds beyond organic chemistry
Organometallic chemistry
In
organometallic chemistry, a coordinatively unsaturated complex has fewer than
18 valence electrons and thus is susceptible to
oxidative addition 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 elect ...
. Unsaturation is characteristic of many
catalysts. The opposite of coordinatively unsaturated is coordinatively saturated. Complexes that are coordinatively saturated rarely exhibit catalytic properties.
Surfaces
In
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, statistica ...
, 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 ot ...
refers to the fraction of
exchangeable cations that are base cations.
References
{{DEFAULTSORT:Unsaturated Compound
Organic chemistry
Chemical nomenclature