IUPAC nomenclature
IUPAC nomenclature is a system of naming
chemical compounds and of describing the science of
chemistry in general. It is developed and kept up to date under the auspices of the
International Union of Pure and Applied Chemistry (IUPAC).
The rules for naming organic and inorganic compounds are contained in two publications, known as the
Blue Book and the
Red Book respectively. A third publication, known as the
Green Book, describes the recommendations for the use of
symbols for
physical quantities (in association with the
IUPAP), while a fourth, the
Gold Book, contains the definitions of a large number of technical terms used in chemistry. Similar compendia exist for biochemistry (in association with the
IUBMB), analytical chemistry and macromolecular chemistry. These books are supplemented by shorter recommendations for specific circumstances which are published from time to time in the
journal Pure and Applied Chemistry.
This article treats the system of nomenclature in general, notably its aims and historical development. Separate articles treat the naming of
organic compounds and
inorganic compounds in more detail.
The primary function of chemical nomenclature is to ensure that the person who hears or reads a chemical name is under no ambiguity as to which chemical compound it refers: each name should refer to a single substance. It is considered less important to ensure that each substance should have a single name, although the number of acceptable names is limited.
It is also preferable that the name convey some information about the structure or chemistry of a compound.
CAS numbers form an extreme example of names which do not perform this function: each refers to a single compound but none contain information about the structure. One might be tempted to add [7647-14-5] to one's meal, but not [133-43-9]—the former is
sodium chloride, the latter
sodium cyanide.
The form of nomenclature which should be used depends on the public to which it is addressed: as such there is no single
correct form, but rather different forms which are more or less appropriate in different circumstances.
A common name will often suffice to identify a chemical compound in a particular set of circumstances. There is little risk that the "salt" on a dinner table will be sodium cyanide (technically a
salt itself)! To be more generally applicable, the name should indicate at least the
chemical formula: hence table salt is referred to chemically as
sodium chloride, which indicates by the rules of
inorganic nomenclature that the formula is NaCl. To be more specific still, the three-dimensional arrangement of the atoms may need to be specified: there are occasions where it might be necessary to distinguish between
sodium chloride (halite structure) (the common form) and
sodium chloride (CsCl structure) (of theoretical interest only). In a few specific circumstances (such as the construction of large indices), it becomes necessary to ensure that each compound has a unique name: this requires the addition of extra rules to the standard IUPAC system (the
CAS system is the most commonly used in this context), at the expense of having names which are longer and less familiar to most readers. Other system gaining popularity is
International Chemical Identifier - InChI - while InChI symbols are not human readable they contain complete information about substance structure. That makes them more general than CAS numbers.
The IUPAC system is often criticized for these above failures when they become relevant (for example in differing reactivity of sulfur allotropes which IUPAC doesn't distinguish). While IUPAC has a human-readable advantage over CAS numbering, it would be difficult to claim that the IUPAC names for some larger, relevant molecules (such as
rapamycin) are human-readable, and so most researchers simply use the informal names.
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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 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 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, and promoted by the latter in a textbook which would survive long after his death at the
guillotine in
1794. The project was also espoused by
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.
Compositional nomenclature
Stock nomenclature
Radical nomenclature
Substitutive nomenclature
Additive nomenclature
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Name*
Nomenclature*
IUPAC nomenclature of organic chemistry*
IUPAC nomenclature of inorganic chemistry*
List of chemical compounds with unusual names#
Nomenclature of Organic Chemistry, Oxford:Pergamon Press, 1979;
A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993, Oxford:Blackwell Scientific Publications, 1993. (ISBN 3540411380)#
Nomenclature of Inorganic Chemistry, Recommendations 1990, Oxford:Blackwell Scientific Publications. (1990) (ISBN 0854044876, 2nd ed)#
Quantities, Units and Symbols in Physical Chemistry (2nd Edn.), Oxford:Blackwell Scientific Publications. (1993)#
Compendium of Chemical Terminology, IUPAC Recommendations (2nd Edn.), Oxford:Blackwell Scientific Publications. (1997)#
Biochemical Nomenclature and Related Documents, London:Portland Press, 1992.#
Compendium of Analytical Nomenclature, Definitive Rules 1997 (3rd Edn.), Oxford:Blackwell Scientific Publications, 1998.#
Compendium of Macromolecular Nomenclature, Oxford:Blackwell Scientific Publications, 1991.# Guyton de Morveau, L. B. (1782).
J. Phys. 19, 310.# Guyton de Morveau, L. B.; Lavoisier, A. L.; Berthollet, C. L.; de Fourcroy, A. F. (1787).
Méthode de Nomenclature Chimique, Paris.# Lavoisier, A. L. (1801).
Traité Elémentaire de Chimie (3e edn.), Paris:Deterville.# Berzelius, J. J. (1811).
J. Phys. 73, 248.#
Bull. Soc. Chim. (Paris) 3(7), xiii. (1892)
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IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the
"Red Book")
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IUPAC Nomenclature of Organic Chemistry (online version of the
"Blue Book")
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IUPAC Recommendations on Organic & Biochemical Nomenclature, Symbols, Terminology, etc. (includes IUBMB Recommendations for biochemistry)
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IUPAC Abbreviated list of quantities, units and symbols in physical chemistry (online version of the
"Green Book")
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IUPAC Compendium of Chemical Terminology (online version of the
"Gold Book", from
IUPAC)
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IUPAC Compendium of Chemical Terminology (online version of the
"Gold Book", from the
RSC, allows free text searching.)
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Find all Chemical Names, Synonyms, CAS, Formula
