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Nomenclatura IUPAC

Este artigo encontra-se parcialmente em língua estrangeira. Ajude e colabore com a tradução.

Nomenclatura IUPAC é um sistema de nomeação de compostos químicos e de se descrever a ciência química em geral. Ela é desenvolvida e mantida atual através da União Internacional de Química Pura e Aplicada (cuja sigla em inglês é IUPAC)

As regras para se nomear compostos orgânicos e inorgânicos estão contidas em duas publicações, conhecidos como Livro Azul 1 e Livro Vermelho 2, respectivamente. Uma terceira publicação, conhecida como Livro Verde 3 descreve as recomendações para o uso dos símbolos de grandezas físicas, enquanto uma quarta publicação, o Livro Dourado 4 contém a definição de uma grande quantidade de termos técnicos utilizados na química. Compêndios similares existem para bioquímica5 (em associação com a IUBMB), química analítica 6 e química macromolecular7. Estes livros são suplementados por recomendações menos extensas para circunstâncias específicas, sendo publicadas de tempos em tempos no Journal of Pure and Apllied Chemistry.

Este artico irá tratar do sistema de nomenclatura em geral, com maior enfoque em seus ideais e desenvolvimento histórico.


Aims of chemical nomenclature

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.


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 recommendations8 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,9 and promoted by the latter in a textbook which would survive long after his death at the guillotine in 1794.10 The project was also espoused by Berzelius,11 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.12

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


Compositional nomenclature

Stock nomenclature

Radical nomenclature

Substitutive nomenclature

Additive nomenclature

See also


  1. ^- Nomenclature of Organic Chemistry, Oxford:Pergamon Press, 1979; A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993, Oxford:Blackwell Scientific Publications, 1993. (ISBN 3-540-41138-0)
  2. ^- Nomenclature of Inorganic Chemistry, Recommendations 1990, Oxford:Blackwell Scientific Publications. (1990) (ISBN 0-85404-487-6, 2nd ed)
  3. ^- Quantities, Units and Symbols in Physical Chemistry (2nd Edn.), Oxford:Blackwell Scientific Publications. (1993)
  4. ^- Compendium of Chemical Terminology, IUPAC Recommendations (2nd Edn.), Oxford:Blackwell Scientific Publications. (1997)
  5. ^- Biochemical Nomenclature and Related Documents, London:Portland Press, 1992.
  6. ^- Compendium of Analytical Nomenclature, Definitive Rules 1997 (3rd Edn.), Oxford:Blackwell Scientific Publications, 1998.
  7. ^- Compendium of Macromolecular Nomenclature, Oxford:Blackwell Scientific Publications, 1991.
  8. ^- Guyton de Morveau, L. B. (1782). J. Phys. 19, 310.
  9. ^- Guyton de Morveau, L. B.; Lavoisier, A. L.; Berthollet, C. L.; de Fourcroy, A. F. (1787). Méthode de Nomenclature Chimique, Paris.
  10. ^- Lavoisier, A. L. (1801). Traité Elémentaire de Chimie (3e edn.), Paris:Deterville.
  11. ^- Berzelius, J. J. (1811). J. Phys. 73, 248.
  12. ^- Bull. Soc. Chim. (Paris) 3(7), xiii. (1892)

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