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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 IUPAC's rules for naming
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
and
inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
s are contained in two publications, known as the '' Blue Book''. . and the '' Red Book'',. respectively. A third publication, known as the '' Green Book'',. recommends the use of
symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
s for
physical quantities A physical quantity is a physical property of a material or system that can be quantified by measurement. A physical quantity can be expressed as a ''value'', which is the algebraic multiplication of a ' Numerical value ' and a ' Unit '. For examp ...
(in association with the
IUPAP The International Union of Pure and Applied Physics (IUPAP ) is an international non-governmental organization whose mission is to assist in the worldwide development of physics, to foster international cooperation in physics, and to help in the ...
), while a fourth, the '' Gold Book'',''Compendium of Chemical Terminology, IMPACT Recommendations (2nd Ed.)'', Oxford:Blackwell Scientific Publications. (1997) defines many technical terms used in chemistry. Similar compendia exist for biochemistry''Biochemical Nomenclature and Related Documents'', London: Portland Press, 1992. (the ''White Book'', in association with the IUBMB), analytical chemistry (the '' Orange Book''), macromolecular chemistry''Compendium of Macromolecular Nomenclature'', Oxford: Blackwell Scientific Publications, 1991. (the ''Purple Book''), and clinical chemistry. (the ''Silver Book''). These "color books" are supplemented by specific recommendations published periodically in the journal ''
Pure and Applied Chemistry ''Pure and Applied Chemistry'' is the official journal for the International Union of Pure and Applied Chemistry (IUPAC). It is published monthly by Walter de Gruyter Walter de Gruyter GmbH, known as De Gruyter (), is a German scholarly publ ...
''.


Aims of chemical nomenclature

The main goal of chemical nomenclature is to disambiguate the spoken or written names of chemical compounds: each name should refer to one compound. Secondarily: each compound should have only one name, although in some cases some alternative names are accepted. Preferably, the name should also reflect the structure or chemistry of a compound. This is achieved by the International Chemical Identifier (InChI) nomenclature. However, the American Chemical Society's CAS numbers nomenclature reflects nothing of the compound's structure. The nomenclature used depends on the needs of the user, so no single correct nomenclature exists. Rather, different nomenclatures suit different circumstances. A
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
will successfully identify a chemical compound, given context. Without context, the name should indicate at least the
chemical composition A chemical composition specifies the identity, arrangement, and ratio of the elements making up a compound. Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for ...
. To be more specific, the name may need to reflect the three-dimensional arrangement of the atoms.This requires adding more rules to the standard IUPAC system (the CAS system is the most commonly used in this context), at the expense of having longer and less familiar names. The IUPAC system is often criticized for the failing to distinguish relevant compounds (for example, in differing reactivity of sulfur allotropes, which IUPAC does not distinguish). While IUPAC has a human-readable advantage over CAS numbering, IUPAC names for some larger, relevant molecules (such as rapamycin) are barely human-readable, so common names are used instead.


Differing aims of chemical nomenclature and lexicography

It is generally understood that the aims of lexicography versus chemical nomenclature vary and are to an extent at odds. Dictionaries of words, whether in traditional print or on the web, collect and report the meanings of words as their uses appear and change over time. For web dictionaries with limited or no formal editorial process, definitions —in this case, definitions of chemical names and terms— can change rapidly without concern for the formal or historical meanings. Chemical nomenclature on the other hand (with IUPAC nomenclature as the best example) is necessarily more restrictive: It aims to standardize communication and practice so that, when a chemical term is used it has a fixed meaning relating to chemical structure, thereby giving insights into chemical properties and derived molecular functions. These differing aims can have profound effects on valid understanding in chemistry, especially with regard to chemical classes that have achieved mass attention. Examples of the impact of these can be seen in considering the examples of: *
resveratrol Resveratrol (3,5,4′-trihydroxy-''trans''-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or when the plant is under attack by pathogens, such as bacteria or fungi. Sources ...
, a single compound clearly defined by this common name, but that can be confused, popularly, with its ''cis''-isomer, * omega-3 fatty acids, a reasonably well-defined chemical structure class that is nevertheless broad as a result of its formal definition, and * polyphenols, a fairly broad structural class with a formal definition, but where mistranslations and general misuse of the term relative to the formal definition has led to serious usage errors, and so ambiguity in the relationship between structure and activity (
SAR SAR or Sar may refer to: Places * Sar (river), Galicia, Spain * Sar, Bahrain, a residential district * Sar, Iran (disambiguation), several places in Iran * Sar, Tibet, Tibet Autonomous Region of China * Šar Mountains, in southeastern Europe ...
). The rapid pace at which meanings can change on the web, in particular for chemical compounds with perceived health benefits, rightly or wrongly ascribed, complicate the monosemy of nomenclature (and so access to SAR understanding). Specific examples appear on the polyphenols article, where varying web and common-use definitions conflict with any accepted chemical nomenclature connecting polyphenol structure and bioactivity).


History

The nomenclature of alchemy is rich in description, but does not effectively meet the aims outlined above. Opinions differ about whether this was deliberate on the part of the early practitioners of alchemy or whether it was a consequence of the particular (and often esoteric) theoretical framework in which they worked. While both explanations are probably valid to some extent, it is remarkable that the first "modern" system of chemical nomenclature appeared at the same time as the distinction (by
Lavoisier Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794),
CNRS (
elements Element or elements may refer to: Science * Chemical element, a pure substance of one type of atom * Heating element, a device that generates heat by electrical resistance * Orbital elements, parameters required to identify a specific orbit of ...
and compounds, in the late eighteenth century. The
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
chemist Louis-Bernard Guyton de Morveau published his recommendations in 1782, hoping that his "constant method of denomination" would "help the intelligence and relieve the memory". The system was refined in collaboration with
Berthollet Claude Louis Berthollet (, 9 December 1748 – 6 November 1822) was a Savoyard-French chemist who became vice president of the French Senate in 1804. He is known for his scientific contributions to theory of chemical equilibria via the mech ...
, de Fourcroy and
Lavoisier Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794),
CNRS (
. and promoted by the latter in a textbook that would survive long after his death at the guillotine in 1794.. The project was also espoused by Jöns Jakob Berzelius,.. who adapted the ideas for the German-speaking world. The recommendations of Guyton covered only what would be today known as inorganic compounds. With the massive expansion of organic chemistry in the mid-nineteenth century and the greater understanding of the structure of organic compounds, the need for a less ''ad hoc'' system of nomenclature was felt just as the theoretical tools became available to make this possible. An international conference was convened in Geneva in 1892 by the national chemical societies, from which the first widely accepted proposals for standardization arose.. A commission was set up in 1913 by the Council of the International Association of Chemical Societies, but its work was interrupted by World War I. After the war, the task passed to the newly formed International Union of Pure and Applied Chemistry, which first appointed commissions for organic, inorganic, and biochemical nomenclature in 1921 and continues to do so to this day.


Types of nomenclature


Organic chemistry

* Substitutive name * Functional class name, also known as a radicofunctional name * Conjunctive name * Additive name * Subtractive name * Multiplicative name * Fusion name * Hantzsch–Widman name * Replacement name


Inorganic chemistry


Compositional nomenclature


= Type-I ionic binary compounds

= For type-I ionic binary compounds, the
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
(a metal in most cases) is named first, and the anion (usually a
nonmetal In chemistry, a nonmetal is a chemical element that generally lacks a predominance of metallic properties; they range from colorless gases (like hydrogen) to shiny solids (like carbon, as graphite). The electrons in nonmetals behave differentl ...
) is named second. The cation retains its elemental name (e.g., ''iron'' or ''zinc''), but the suffix of the nonmetal changes to ''-ide''. For example, the compound is made of cations and anions; thus, it's called lithium bromide. The compound , which is composed of cations and anions, is referred to as barium oxide. The oxidation state of each element is unambiguous. When these ions combine into a type-I binary compound, their equal-but-opposite charges are neutralized, so the compound's net charge is zero.


= Type-II ionic binary compounds

= Type-II ionic binary compounds are those in which the cation does not have just one oxidation state. This is common among
transition metals In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
. To name these compounds, one must determine the charge of the cation and then write out the name as would be done with Type-I ionic compounds, except that a Roman numeral (indicating the charge of the cation) is written in parentheses next to the cation name (this is sometimes referred to as
Stock nomenclature Stock nomenclature for inorganic compounds is a widely used system of chemical nomenclature developed by the German chemist Alfred Stock and first published in 1919. In the "Stock system", the oxidation states of some or all of the elements in a ...
). For example, take the compound . The cation, iron, can occur as and . In order for the compound to have a net charge of zero, the cation must be so that the three anions can be balanced out (3+ and 3− balance to 0). Thus, this compound is called
iron(III) chloride Iron(III) chloride is the inorganic compound with the formula . Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The col ...
. Another example could be the compound . Because the anion has a subscript of 2 in the formula (giving a 4− charge), the compound must be balanced with a 4+ charge on the cation ( lead can form cations with a 4+ or a 2+ charge). Thus, the compound is made of one cation to every two anions, the compound is balanced, and its name is written as
lead(IV) sulfide Lead(IV) sulfide is a chemical compound with the formula Pb S2. This material is generated by the reaction of the more common lead(II) sulfide, PbS, with sulfur at >600 °C and at high pressures. PbS2, like the related tin(IV) sulfide SnS2, cryst ...
. An older system – relying on Latin names for the elements – is also sometimes used to name Type-II ionic binary compounds. In this system, the metal (instead of a Roman numeral next to it) has an "-ic" or "-ous" suffix added to it to indicate its oxidation state ("-ous" for lower, "-ic" for higher). For example, the compound contains the cation (which balances out with the anion). Since this oxidation state is lower than the other possibility (), this compound is sometimes called ferrous oxide. For the compound, , the tin ion is (balancing out the 4− charge on the two anions), and because this is a higher oxidation state than the alternative (), this compound is called
stannic oxide Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names, this oxide of tin is an important material in tin ...
. Some ionic compounds contain polyatomic ions, which are charged entities containing two or more covalently bonded types of atoms. It is important to know the names of common polyatomic ions; these include: *
ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...
() *
nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
() *
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
() *
sulfite Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are wide ...
() * sulfate () *
hydrogen sulfate The sulfate or sulphate ion is a polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), ...
(bisulfate) () * hydroxide () *
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of a ...
() * phosphate () * hydrogen phosphate () * dihydrogen phosphate () * carbonate () *
hydrogen carbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemica ...
(bicarbonate) () *
hypochlorite In chemistry, hypochlorite is an anion with the chemical formula ClO−. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite (a component of ble ...
() *
chlorite The chlorite ion, or chlorine dioxide anion, is the halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as salts of chlorous ac ...
() *
chlorate The chlorate anion has the formula ClO3-. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by ...
() * perchlorate () *
acetate An acetate is a salt (chemistry), salt formed by the combination of acetic acid with a base (e.g. Alkali metal, alkaline, Alkaline earth metal, earthy, Transition metal, metallic, nonmetallic or radical Radical (chemistry), base). "Acetate" als ...
() * permanganate () * dichromate () * chromate () * peroxide () * superoxide () * oxalate () *
hydrogen oxalate Hydrogenoxalate or hydrogen oxalate is an anion with chemical formula or , derived from oxalic acid by the loss of a single proton; or, alternatively, from the oxalate anion by addition of a proton. The name is also used for any salt containing ...
() The formula denotes that the cation is sodium, or , and that the anion is the sulfite ion (). Therefore, this compound is named sodium sulfite. If the given formula is , it can be seen that is the hydroxide ion. Since the charge on the calcium ion is 2+, it makes sense there must be two ions to balance the charge. Therefore, the name of the compound is
calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed or slaked with water. It has m ...
. If one is asked to write the formula for copper(I) chromate, the Roman numeral indicates that copper ion is and one can identify that the compound contains the chromate ion (). Two of the 1+ copper ions are needed to balance the charge of one 2− chromate ion, so the formula is .


= Type-III binary compounds

= Type-III binary compounds are covalently bonded. Covalent bonding occurs between nonmetal elements. Covalently-bonded compounds are also known as '' molecules''. In the compound, the first element is named first and with its full elemental name. The second element is named as if it were an anion (root name of the element + ''-ide'' suffix). Then, prefixes are used to indicate the numbers of each atom present: these prefixes are ''mono-'' (one), ''di-'' (two), ''tri-'' (three), ''tetra-'' (four), ''penta-'' (five), ''hexa-'' (six), ''hepta-'' (seven), ''octa-'' (eight), ''nona-'' (nine), and ''deca-'' (ten). The prefix ''mono-'' is never used with the first element. Thus, is called
nitrogen trichloride Nitrogen trichloride, also known as trichloramine, is the chemical compound with the formula NCl3. This yellow, oily, pungent-smelling and explosive liquid is most commonly encountered as a byproduct of chemical reactions between ammonia-derivative ...
, is called
diphosphorus pentaoxide Diphosphorus is an inorganic chemical with the chemical formula . Unlike nitrogen, its lighter pnictogen neighbor which forms a stable N2 molecule with a nitrogen to nitrogen triple bond, phosphorus prefers a tetrahedral form P4 because P-P pi-bo ...
(the ''a'' of the ''penta-'' prefix is not dropped before the vowel. As the IUPAC Red Book 2005 page 69 states, "The final vowels of multiplicative prefixes should not be elided (although "monoxide", rather than "monooxide", is an allowed exception because of general usage."), and is called
boron trifluoride Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. Structure and bondin ...
. Carbon dioxide is written ;
sulfur tetrafluoride Sulfur tetrafluoride is the chemical compound with the formula S F4. It is a colorless corrosive gas that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound is a useful reagent for t ...
is written . A few compounds, however, have common names that prevail. , for example, is usually called '' water'' rather than ''
dihydrogen monoxide The dihydrogen monoxide parody involves calling water by an unfamiliar chemical name, most often "dihydrogen monoxide" (DHMO), and listing some of water's properties in a particularly alarming manner, such as accelerating corrosion (rust) and ...
'', and is preferentially called '' ammonia'' rather than ''nitrogen trihydride''.


Substitutive nomenclature

This naming method generally follows established IUPAC organic nomenclature.
Hydrides In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of ...
of the main group elements (groups 13–17) are given ''-ane'' base name, e.g. borane (), oxidane (),
phosphane Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting f ...
() (Although the name '' phosphine'' is also in common use, it is not recommended by IUPAC). The compound would thus be named substitutively as trichlorophosphane (with chlorine "substituting"). However, not all such names (or stems) are derived from the element name. For example, is called " azane".


Additive nomenclature

This naming method has been developed principally for coordination compounds although it can be more widely applied. An example of its application is , pentaamminechloridocobalt(III) chloride. Ligands, too, have a special naming convention. Whereas ''chloride'' becomes the prefix ''chloro-'' in substitutive naming, in a ligand it becomes ''chlorido-''.


See also

* IUPAC nomenclature of inorganic chemistry 2005 * IUPAC nomenclature of organic chemistry * Preferred IUPAC name * IUPAC numerical multiplier *
IUPAC nomenclature for organic transformations The IUPAC Nomenclature for Transformations is a methodology for naming a chemical reaction. Traditionally a chemical reaction especially in organic chemistry is named after its inventor, the so-called name reaction, to name just a few: Knoevenagel ...
* International Chemical Identifier * List of chemical compounds with unusual names


References


External links

* Interactiv
IUPAC Compendium of Chemical Terminology
(interactive "Gold Book")

(list of all IUPAC nomenclature books, and means of accessing them)

("''Gold Book''")

("''Green Book''")
IUPAC Nomenclature of Organic Chemistry
("''Blue Book''")

("''Red Book''")
IUPAC Recommendations on Organic & Biochemical Nomenclature, Symbols, Terminology, etc.
(includes IUBMB Recommendations for biochemistry)
chemicalize.org
A free web site/service that extracts IUPAC names from web pages and annotates a "chemicalized" version with structure images. Structures from annotated pages can also be searched.
ChemAxon Name <> Structure
– IUPAC (& traditional) name to structure and structure to IUPAC name software. As used a
chemicalize.org

ACD/Name
– Generates IUPAC, INDEX (CAS), InChi, Smiles, etc. for drawn structures in 10 languages and translates names to structures. Also available as batch tool and for Pipeline Pilot. Part of
I-Lab 2.0
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