Chemical nomenclature

Last updated

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).

Contents

The IUPAC's rules for naming organic and inorganic compounds are contained in two publications, known as the Blue Book [1] [2] and the Red Book , [3] respectively. A third publication, known as the Green Book , [4] recommends the use of symbols for physical quantities (in association with the IUPAP), while a fourth, the Gold Book , [5] defines many technical terms used in chemistry. Similar compendia exist for biochemistry [6] (the White Book, in association with the IUBMB), analytical chemistry [7] (the Orange Book ), macromolecular chemistry [8] (the Purple Book), and clinical chemistry [9] (the Silver Book). These "color books" are supplemented by specific recommendations published periodically in the journal Pure and Applied Chemistry .

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 will successfully identify a chemical compound, given context. Without context, the name should indicate at least the chemical composition. 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:

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

First page of Lavoisier's Chymical Nomenclature in English. Lavoisier Nomenclature01.gif
First page of Lavoisier's Chymical Nomenclature in English.

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) between elements and compounds, in the late eighteenth century.

The French chemist Louis-Bernard Guyton de Morveau published his recommendations [10] 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, de Fourcroy and Lavoisier, [11] and promoted by the latter in a textbook that would survive long after his death at the guillotine in 1794. [12] The project was also espoused by Jöns Jakob Berzelius, [13] [14] 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. [15]

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

Inorganic chemistry

Compositional nomenclature

Type-I ionic binary compounds

For type-I ionic binary compounds, the cation (a metal in most cases) is named first, and the anion (usually a nonmetal) 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 LiBr is made of Li+ cations and Br− anions; thus, it's called lithium bromide. The compound BaO, which is composed of Ba2+ cations and O2− 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. 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). For example, take the compound FeCl3. The cation, iron, can occur as Fe2+ and Fe3+. In order for the compound to have a net charge of zero, the cation must be Fe3+ so that the three Cl− anions can be balanced out (3+ and 3− balance to 0). Thus, this compound is called iron(III) chloride. Another example could be the compound PbS2. Because the S2− anion has a subscript of 2 in the formula (giving a 4− charge), the compound must be balanced with a 4+ charge on the Pb cation (lead can form cations with a 4+ or a 2+ charge). Thus, the compound is made of one Pb4+ cation to every two S2− anions, the compound is balanced, and its name is written as lead(IV) sulfide.

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 FeO contains the Fe2+ cation (which balances out with the O2− anion). Since this oxidation state is lower than the other possibility (Fe3+), this compound is sometimes called ferrous oxide. For the compound, SnO2, the tin ion is Sn4+ (balancing out the 4− charge on the two O2− anions), and because this is a higher oxidation state than the alternative (Sn2+), this compound is called stannic oxide.

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:

The formula Na2SO3 denotes that the cation is sodium, or Na+, and that the anion is the sulfite ion (SO2−3). Therefore, this compound is named sodium sulfite. If the given formula is Ca(OH)2, it can be seen that OH− is the hydroxide ion. Since the charge on the calcium ion is 2+, it makes sense there must be two OH− ions to balance the charge. Therefore, the name of the compound is calcium hydroxide. If one is asked to write the formula for copper(I) chromate, the Roman numeral indicates that copper ion is Cu+ and one can identify that the compound contains the chromate ion (CrO2−4). Two of the 1+ copper ions are needed to balance the charge of one 2− chromate ion, so the formula is Cu2CrO4.

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, NCl3 is called nitrogen trichloride, P2O5 is called diphosphorus pentaoxide (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 BF3 is called boron trifluoride.

Carbon dioxide is written CO2; sulfur tetrafluoride is written SF4. A few compounds, however, have common names that prevail. H2O, for example, is usually called water rather than dihydrogen monoxide , and NH3 is preferentially called ammonia rather than nitrogen trihydride.

Substitutive nomenclature

This naming method generally follows established IUPAC organic nomenclature. Hydrides of the main group elements (groups 13–17) are given -ane base name, e.g. borane ( B H 3), oxidane ( H 2 O ), phosphane ( P H 3) (Although the name phosphine is also in common use, it is not recommended by IUPAC). The compound P Cl 3 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, N H 3 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 [CoCl(NH3)5]Cl2, 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

Related Research Articles

<span class="mw-page-title-main">Coordination complex</span> Molecule or ion containing ligands datively bonded to a central metallic atom

A coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals, are coordination complexes.

<span class="mw-page-title-main">Functional group</span> Set of atoms in a molecule which augment its chemical and/or physical properties

In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition. This enables systematic prediction of chemical reactions and behavior of chemical compounds and the design of chemical synthesis. The reactivity of a functional group can be modified by other functional groups nearby. Functional group interconversion can be used in retrosynthetic analysis to plan organic synthesis.

<span class="mw-page-title-main">Inorganic chemistry</span> Field of chemistry

Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.

In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively charged sodium ions and negatively charged chloride ions.

In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. While fully ionic bonds are not found in nature, many bonds exhibit strong ionicity, making oxidation state a useful predictor of charge.

<span class="mw-page-title-main">Acyl group</span> Chemical group (R–C=O)

In chemistry, an acyl group is a moiety derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids. It contains a double-bonded oxygen atom and an alkyl group. In organic chemistry, the acyl group is usually derived from a carboxylic acid, in which case it has the formula RCO−, where R represents an alkyl group that is linked to the carbon atom of the group by a single bond. Although the term is almost always applied to organic compounds, acyl groups can in principle be derived from other types of acids such as sulfonic acids and phosphonic acids. In the most common arrangement, acyl groups are attached to a larger molecular fragment, in which case the carbon and oxygen atoms are linked by a double bond.

<span class="mw-page-title-main">Sulfate</span> Oxyanion with a central atom of sulfur surrounded by 4 oxygen atoms

The sulfate or sulphate ion is a polyatomic anion with the empirical formula SO2−4. Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many are prepared from that acid.

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 nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

<span class="mw-page-title-main">Ionic compound</span> Chemical compound involving ionic bonding

In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions. These can be simple ions such as the sodium (Na+) and chloride (Cl−) in sodium chloride, or polyatomic species such as the ammonium (NH+
4) and carbonate (CO2−
3) ions in ammonium carbonate. Individual ions within an ionic compound usually have multiple nearest neighbours, so are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Ionic compounds usually form crystalline structures when solid.

<span class="mw-page-title-main">Sulfide</span> Ion, and compounds containing the ion

Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide.

An oxyanion, or oxoanion, is an ion with the generic formula A
xOz−
y. Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H
zA
xO
y. The structures of condensed oxyanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra. The oxyanions adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology.

In chemistry, the valence or valency of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.

<span class="mw-page-title-main">Radical anion</span> Free radical species

In organic chemistry, a radical anion is a free radical species that carries a negative charge. Radical anions are encountered in organic chemistry as reduced derivatives of polycyclic aromatic compounds, e.g. sodium naphthenide. An example of a non-carbon radical anion is the superoxide anion, formed by transfer of one electron to an oxygen molecule. Radical anions are typically indicated by .

In chemistry an antimonate is a compound which contains a metallic element, oxygen, and antimony in an oxidation state of +5. These compounds adopt polymeric structures with M-O-Sb linkages. They can be considered to be derivatives of the hypothetical antimonic acid H3SbO4, or combinations of metal oxides and antimony pentoxide, Sb2O5.

In chemical nomenclature, the IUPAC nomenclature of inorganic chemistry is a systematic method of naming inorganic chemical compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It is published in Nomenclature of Inorganic Chemistry. Ideally, every inorganic compound should have a name from which an unambiguous formula can be determined. There is also an IUPAC nomenclature of organic chemistry.

An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce the H+ cation and the anion of the acid.

<span class="mw-page-title-main">Bridging ligand</span> Ligand which connects two or more (usually metal) atoms in a coordination complex

In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are specifically designed to link two metals.

<span class="mw-page-title-main">Layered double hydroxides</span> Class of ionic solids characterized by a layered structure

Layered double hydroxides (LDH) are a class of ionic solids characterized by a layered structure with the generic layer sequence [AcB Z AcB]n, where c represents layers of metal cations, A and B are layers of hydroxide anions, and Z are layers of other anions and neutral molecules. Lateral offsets between the layers may result in longer repeating periods.

In chemistry, an ate complex is a salt formed by the reaction of a Lewis acid with a Lewis base whereby the central atom increases its valence and gains a negative formal charge..

Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of Nomenclature of Inorganic Chemistry. It is a collection of rules for naming inorganic compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).

References

  1. ↑ "1958 (A: Hydrocarbons, and B: Fundamental Heterocyclic Systems), 1965 (C: Characteristic Groups)", Nomenclature of Organic Chemistry (3rd ed.), London: Butterworths, 1971, ISBN   978-0-408-70144-0 .
  2. ↑ Rigaudy, J.; Klesney, S. P., eds. (1979). Nomenclature of Organic Chemistry . IUPAC/Pergamon Press. ISBN   0-08022-3699.. Panico R, Powell WH, Richer JC, eds. (1993). A Guide to IUPAC Nomenclature of Organic Compounds . IUPAC/Blackwell Science. ISBN   0-632-03488-2.. IUPAC, Chemical Nomenclature and Structure Representation Division (27 October 2004). Nomenclature of Organic Chemistry (Provisional Recommendations). IUPAC.
  3. ↑ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC – IUPAC . ISBN   0-85404-438-8 . Electronic version..
  4. ↑ International Union of Pure and Applied Chemistry (1993). Quantities, Units and Symbols in Physical Chemistry , 2nd edition, Oxford: Blackwell Science. ISBN   0-632-03583-8 . Electronic version..
  5. ↑ Compendium of Chemical Terminology, IMPACT Recommendations (2nd Ed.), Oxford:Blackwell Scientific Publications. (1997)
  6. ↑ Biochemical Nomenclature and Related Documents, London: Portland Press, 1992.
  7. ↑ International Union of Pure and Applied Chemistry (1998). Compendium of Analytical Nomenclature (definitive rules 1997, 3rd. ed.). Oxford: Blackwell Science. ISBN   0-86542-6155 .
  8. ↑ Compendium of Macromolecular Nomenclature, Oxford: Blackwell Scientific Publications, 1991.
  9. ↑ Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences, IMPACT Recommendations 1995, Oxford: Blackwell Science, 1995, ISBN   978-0-86542-612-2 .
  10. ↑ Guyton de Morveau, L. B. (1782), "Mémoire sur les dénominations chimiques, la necessité d'en perfectionner le système et les règles pour y parvenir", Observations Sur la Physique, 19: 370–382
  11. ↑ Guyton de Morveau, L. B.; Lavoisier, A. L.; Berthollet, C. L.; Fourcroy, A. F. de (1787), Méthode de Nomenclature Chimique, Paris: Cuchet, archived from the original on 2011-07-21.
  12. ↑ Lavoisier, A. L. (1801), Traité Élémentaire de Chimie (3e ed.), Paris: Deterville.
  13. ↑ Berzelius, J. J. (1811), "Essai sur la nomenclature chimique", Journal de Physique, 73: 253–286.
  14. ↑ Wisniak, Jaime (2000), "Jöns Jacob Berzelius A Guide to the Perplexed Chemist", The Chemical Educator, 5 (6): 343–50, doi:10.1007/s00897000430a, S2CID   98774420 .
  15. ↑ "Congrès de nomenclature chimique, Genève 1892", Bulletin de la Société Chimique de Paris, Série 3, 8: xiii–xxiv, 1892.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.