Английская Википедия:Chemical nomenclature

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Шаблон:Short description 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).

IUPAC Nomenclature ensures that each compound (and its various isomers) have only one formally accepted name known as Systematic IUPAC name, however, some compounds may have alternative names that are also accepted, known as Recommended IUPAC name which is generally taken from the Common/ Trivial/ Historical name of that compound. Preferably, the name should also represent the structure or chemistry of a compound.

For example, the main constituent of white vinegar is CH3COOH, which is commonly called, Acetic acid and is also its Recommended IUPAC name, but its formal, Systematic IUPAC name is Ethanoic acid.

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.

Purpose of chemical nomenclature

The main purpose 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 represent 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 does not represent a compound's structure.

The nomenclature used depends on the needs of the user, so no single correct nomenclature exists. Rather, different nomenclatures are appropriate for 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 represent the three-dimensional arrangement of the atoms. This requires adding more rules to the standard IUPAC system (the Chemical Abstracts Service system (CAS system) is the one used most commonly in this context), at the expense of having names which are longer and less familiar.

The IUPAC system is often criticized for failing to distinguish relevant compounds (for example, for 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 needs of chemical nomenclature and lexicography

It is generally understood that the purposes of lexicography versus chemical nomenclature vary and are to an extent at odds. Dictionaries of words, whether in traditional print or on the internet, collect and report the meanings of words as their uses appear and change over time. For internet 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 however (with IUPAC nomenclature as the best example) is necessarily more restrictive: Its purpose is 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 purposes can affect understanding, especially with regard to chemical classes that have achieved popular attention. Examples of the effect of these are as follows:

  • resveratrol, a single compound defined clearly by this common name, but that can be confused, popularly, with its cis-isomer,
  • omega-3 fatty acids, a reasonably well-defined class of chemical structures 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 resulted in serious errors of usage, and so ambiguity in the relationship between structure and activity (SAR).

The rapid pace at which meanings can change on the internet, in particular for chemical compounds with perceived health benefits, ascribed rightly or wrongly, complicate the monosemy of nomenclature (and so access to SAR understanding). Specific examples appear in the polyphenols article, where varying internet and common-use definitions conflict with any accepted chemical nomenclature connecting polyphenol structure and bioactivity).

History

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

The nomenclature of alchemy is descriptive, but does not effectively represent the functions mentioned 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) theories according to 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, during 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 by guillotine in 1794.[12] The project was also endorsed by Jöns Jakob Berzelius,[13][14] who adapted the ideas for the German-speaking world.

The recommendations of Guyton were only for what would be known now as inorganic compounds. With the massive expansion of organic chemistry during 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 basis 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 developed.[15]

A commission was established 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

Nomenclature has been developed for both organic and inorganic chemistry. There are also designations having to do with structureШаблон:Sndsee Descriptor (chemistry).

Organic chemistry

Шаблон:Main article

  • 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

Шаблон:Main article

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 Шаблон:Chem2 is made of Шаблон:Chem2 cations and Шаблон:Chem2 anions; thus, it is called lithium bromide. The compound Шаблон:Chem2, which is composed of Шаблон:Chem2 cations and Шаблон:Chem2 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 render 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, for the compound Шаблон:Chem2, the cation, iron, can occur as Шаблон:Chem2 and Шаблон:Chem2. In order for the compound to have a net charge of zero, the cation must be Шаблон:Chem2 so that the three Шаблон:Chem2 anions can be balanced (3+ and 3− balance to 0). Thus, this compound is termed iron(III) chloride. Another example could be the compound Шаблон:Chem2. Because the Шаблон:Chem2 anion has a subscript of 2 in the formula (giving a 4− charge), the compound must be balanced with a 4+ charge on the Шаблон:Chem2 cation (lead can form cations with a 4+ or a 2+ charge). Thus, the compound is made of one Шаблон:Chem2 cation to every two Шаблон:Chem2 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 a suffix "-ic" or "-ous" added to it to indicate its oxidation state ("-ous" for lower, "-ic" for higher). For example, the compound Шаблон:Chem2 contains the Шаблон:Chem2 cation (which balances out with the Шаблон:Chem2 anion). Since this oxidation state is lower than the other possibility (Шаблон:Chem2), this compound is sometimes called ferrous oxide. For the compound, Шаблон:Chem2, the tin ion is Шаблон:Chem2 (balancing out the 4− charge on the two Шаблон:Chem2 anions), and because this is a higher oxidation state than the alternative (Шаблон:Chem2), this compound is termed 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 Шаблон:Chem2 denotes that the cation is sodium, or Шаблон:Chem2, and that the anion is the sulfite ion (Шаблон:Chem2). Therefore, this compound is named sodium sulfite. If the given formula is Шаблон:Chem2, it can be seen that Шаблон:Chem2 is the hydroxide ion. Since the charge on the calcium ion is 2+, it makes sense there must be two Шаблон:Chem2 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 Шаблон:Chem2 and one can identify that the compound contains the chromate ion (Шаблон:Chem2). Two of the 1+ copper ions are needed to balance the charge of one 2− chromate ion, so the formula is Шаблон:Chem2.

Type-III binary compounds

Type-III binary compounds are bonded covalently. Covalent bonding occurs between nonmetal elements. Compounds bonded covalently are also known as molecules. For 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 (base 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, Шаблон:Chem2 is termed nitrogen trichloride, Шаблон:Chem2 is termed boron trifluoride, and Шаблон:Chem2 is termed diphosphorus pentoxide (although the a of the prefix penta- should actually not be omitted before a vowel: 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).").

Carbon dioxide is written Шаблон:Chem2; sulfur tetrafluoride is written Шаблон:Chem2. A few compounds, however, have common names that prevail. Шаблон:Chem2, for example, is usually termed water rather than dihydrogen monoxide, and Шаблон:Chem2 is preferentially termed 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 the base name ending with -ane, e.g. borane (Шаблон:Chem2), oxidane (Шаблон:Chem2), phosphane (Шаблон:Chem2) (Although the name phosphine is also in common use, it is not recommended by IUPAC). The compound Шаблон:Chem2 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, Шаблон:Chem2 is termed "azane".

Additive nomenclature

This method of naming has been developed principally for coordination compounds although it can be applied more widely. An example of its application is Шаблон:Chem2, pentaamminechloridocobalt(III) chloride.

Ligands, too, have a special naming convention. Whereas chloride becomes the prefix chloro- in substitutive naming, for a ligand it becomes chlorido-.

See also

References

Шаблон:Reflist [16] [17] [18]

External links

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  1. ↑ Шаблон:Citation.
  2. ↑ Шаблон:BlueBook1979. Шаблон:BlueBook1993. Шаблон:BlueBook2004
  3. ↑ Шаблон:RedBook2005.
  4. ↑ Шаблон:GreenBook2nd.
  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. ↑ Шаблон:OrangeBook3rd
  8. ↑ Compendium of Macromolecular Nomenclature, Oxford: Blackwell Scientific Publications, 1991.
  9. ↑ Шаблон:Citation.
  10. ↑ Шаблон:Citation
  11. ↑ Шаблон:Citation.
  12. ↑ Шаблон:Citation.
  13. ↑ Шаблон:Citation.
  14. ↑ Шаблон:Citation.
  15. ↑ Шаблон:Citation.
  16. ↑ Шаблон:Cite journal
  17. ↑ Шаблон:Cite journal
  18. ↑ Шаблон:Cite journal
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