Wikipedia:Naming conventions (chemistry)

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General rule

From Wikipedia:Naming conventions:

Generally, article naming should give priority to what the majority of English speakers would most easily recognize, with a reasonable minimum of ambiguity, while at the same time making linking to those articles easy and second nature.

Organic compound names

Trivial names (non-systematic, or "common" names) are favored for use in titles of articles for organic compounds instead of systematic names. Trivial names are usually different from the preferred name following IUPAC nomenclature. For compounds lacking trivial names, as is often the case for complex structures, substitutive nomenclature or other systematic names may be used. The general rule is to use the name most commonly used to refer to the compound, as evidenced by use in reliable sources (in line with WP:COMMONNAME).

Classes of compounds may have more specific guidance on naming, such as the use of international nonproprietary names for pharmaceutical compounds (see WP:NCMED and below).

Examples of use of trivial names and not systematic names include:

acetic acid not ethanoic acid
toluene not methylbenzene
lysine not 2,6-diaminohexanoic acid
1-pentanol not pentan-1-ol
benzaldehyde not benzenecarbaldehyde
diethyl ether not ethoxyethane
benzophenone not diphenylmethanone

Systematic and other accepted names for the compound not used as the article title should instead be redirects tagged with the {{R from alternative name}} template and listed in the chembox as other names, with especially significant alternative names mentioned in the lede in bold font.

Element names

Traditionally, the names of three elements have been spelled differently in different parts of the English speaking world. For articles about chemistry-related topics, Wikipedia follows the spellings recommended by the International Union of Pure and Applied Chemistry (IUPAC):[1][2]

aluminium not aluminum
sulfur not sulphur
caesium not cesium

These spellings should be used in all chemistry-related articles on English Wikipedia, even if they conflict with the other national spelling varieties used in the article.

This convention should also be applied to all compounds and derivative names of these chemicals: sulfate not sulphate; sulfuric not sulphuric; etc.

Capitalization of elements and compounds

In former versions of the IUPAC recommendations, names were written with a capital initial letter. This practice has been abandoned in later publications.[3] The names of chemical compounds and chemical elements when written out, are common nouns in English, rather than proper nouns. They are capitalized at the beginning of a sentence or title, but not elsewhere. Note that for chemical elements this applies to the word only and not the chemical symbol, which is always capitalized. Both rules remain even with chemical elements derived from proper names which would otherwise be capitalized, in keeping with IUPAC policy to differentiate proper names from things named after proper names. Thus, it is californium but the symbol is Cf, and einsteinium, but symbol Es. Note that names for odd or rare chemicals are uncapitalized like common ones, and thus uranium and plutonium (symbols U and Pu) should be uncapitalized like carbon or iron (symbols C and Fe). This rule (full name uncapitalized but symbol capitalized) applies also to isotopes and nuclides, when completely written out: thus 14C but carbon-14. (The element mercury is uncapitalized, but of course the planet and god Mercury remain capitalized proper nouns).

Likewise, the names of chemical compounds are considered common nouns which are capitalized at the beginning of a sentence or title, but not elsewhere. Prefixes such as sec-, tert-, ortho-, meta-, para-, α-, β-, D-, L-, (+)-, (−)-, (R)-, (S)- and the numerical prefixes are not considered part of the name: the first letter of the main part of the name should still be capitalized where appropriate. Exceptions are cyclo, iso, neo, and spiro which are considered part of the name and therefore not italicized or hyphenated. Substituent groups do form part of the name: hence we use 2-Aminoethanol at the start of a sentence and 2-aminoethanol if not at the start of a sentence. Note that in this case the two wikilinks refer to separate redirects to the actual article. The article title itself is capitalized.

Prefixes in titles

When the chosen article title starts with a prefix including positional identifiers (ortho-, meta-, para-, N-, O-, α-, β-, γ-, etc.), isomeric identifiers (sec-, tert-, etc.), stereochemical identifiers (cis-, trans-, (E)-, (Z)-, etc.), chiral identifiers ((R)-, (S)-, D-, L-, (+)-, (−)-, etc.), or numbers, the first letter after the prefix in the name should be capitalized: hence titlecase 1,1,1-Trichloroethane not 1,1,1-trichloroethane. A redirect from the uncapitalized version should be created to simplify linking from other articles.

Non-numerical prefixes are italicized and uncapitalized in titles (tert-Butyl alcohol, for example). Both numerical and non-numerical prefixes are followed by a hyphen. The template {{DISPLAYTITLE}} is used to display titles which start with lowercase letters or include italics.

Note that cyclo, iso, neo, and spiro are considered part of a chemical name (such as isopropanol) and not considered prefixes. No hyphens or italics are used in these cases.

Article titles for compounds and related topics should reflect how the compound name is commonly written and use Greek letter prefixes if appropriate, e.g. Α-Ketoglutaric acid, using {{DISPLAYTITLE}} to display as α-Ketoglutaric acid, not Alpha-Ketoglutaric acid and displaying as alpha-Ketoglutaric acid. In the article page name (article location) it is important to use the uppercase Greek letter, which can be easily confused with uppercase Latin letters in many cases, so that DISPLAYTITLE (or alternatively, {{lowercase title}}) will work properly. It is also essential to ensure redirects exist for all possible typed variations of the compound name so searchers can easily reach the appropriate article.

Use of Stock nomenclature

Stock nomenclature for inorganic compounds is based on the indication of the oxidation number (as a roman numeral, in parentheses) of each of the major elements in the compound, e.g. iron(III) chloride. It is widely, if sometimes incorrectly, used on Wikipedia for the titles of articles about inorganic compounds. It is not obligatory, as there are other acceptable methods for naming these compounds, but it is often preferred as the most common non-ambiguous name for a substance. The following guidelines are based on current WikiBestPractice:

  1. Only the cationic element (i.e. the element whose name appears unchanged in the compound name) is assigned its oxidation number. Except in rare cases (none at present), we do not assign the oxidation number in the anion: hence potassium permanganate not potassium manganate(VII), sodium hypochlorite not sodium chlorate(I).
  2. There is no space between the end of the element name and the opening parenthesis: hence silver(I) fluoride not silver (I) fluoride. Note that this is an exception to the usual English style for parentheses.
  3. It is not necessary to specify the oxidation number when there is no possibility of ambiguity in the compound title: hence sodium chloride not sodium(I) chloride.
  4. Stock nomenclature should only be used for ionic compounds. Compounds with a substantial degree of covalency should be named by stoichiometric nomenclature: hence titanium tetrachloride not titanium(IV) chloride.

Isotope labelling

Isotopes when written out are common nouns, and should begin with the uncapitalized element name, followed by a hyphen (not an em dash or en dash) and then the mass number. Examples are carbon-14 and uranium-235. The uncapitalized name of elements when written out (but not in symbol form) follows IUPAC convention for chemical elements, and is not changed when the isotope is written out. See Connelly, N.G.; Damhus, T.; Hartshorn, R.M.; Hutton, A.T., eds. (2005). Nomenclature of Inorganic Chemistry (PDF). RSCIUPAC. ISBN 0-85404-438-8.

For chemical reactions concerning specific isotopes, identify the isotope by its mass number (A). For example, 14C or 18F. You may use a nuclide template. Deuterium and tritium may be labelled "D", "2D", or "2H" and so on. Deuterated solvents for NMR use are customarily described variously as: CD3OD, methanol-d4; CD3SOCD3, DMSO-d6. These established systems are all acceptable, but should remain consistent within an article.

Drug-related articles

Where a compound has a WHO international nonproprietary name (INN), this should be used as the article title (see WP:NCMED). Exceptions would be where the pharmaceutical use of a certain compound is secondary to other applications (commodity chemical, synthetic intermediate, etc., agriculture or industry).


From Wikipedia:Deletion policy: "Don't worry, redirects are cheap."

Redirects should be created for:

  • Alternative names for the compound, including acronyms where appropriate;
  • Alternative capitalizations, where there is a numerical prefix in the article title;
  • Formulas of simple compounds; for example H2Owater.


Even with the best will in the world, no set of guidelines can cover every case. Some articles on Wikipedia have non-standard titles through consensus that this is the most commonly used name (in scientific circumstances) for the compound concerned, whatever IUPAC or the other rules suggest. For example:

ethylene oxide not oxirane
phosphine not phosphane (and for substituted phosphines, arsine, stibine, and bismuthine)
Wilkinson's catalyst not chlorotris(triphenylphosphane)rhodium
Vaska's complex not carbonylchlorobis(triphenylphosphane)iridium
titin not methionylthreonylthreonylglutaminylalanyl...isoleucine[4]

Please do not get into revert wars over the naming of an article: the best place for discussion is on the article's talk page or (failing that) at Wikipedia talk:WikiProject Chemicals.

Groups of compounds

Organic compound classes and functional groups

For articles about classes of organic compounds, the singular class name from the IUPAC "Glossary of Class Names"[5] is usually used, e.g. alkane, carboxylic acid, ether, ketone, acyl chloride. Articles about functional groups should use the name most commonly used to refer to the group in reliable sources (generally, the name of the corresponding radical) followed by the word "group", e.g. alkyl group, carboxyl group, phenyl group, carbonyl group, trimethylsilyl group, triflyl group. In many cases, the compound or compound class and corresponding functional group are discussed in the same article, generally using the compound class as the article title with the name(s) of the functional group redirecting there (although the opposite is possible).

For groups of compounds named after a simple parent compound, articles about the group should be located at the plural of the parent compound name, e.g. hydrazines, silanes, boranes, diphosphenes. Similarly, salts and esters of carboxylic acids should collectively be referred to by the plural of the carboxylate. In some cases, the group of compounds (e.g. triflates), the functional group (e.g. triflate group), and the carboxylate (e.g. triflate) will warrant a separate article; whether the article should be titled by the compound group, functional group, or carboxylate should be decided on a case by case basis depending on the group and how the article is constructed. Related terms not chosen as the title should be redirects and mentioned in the lede in bold font. In cases where the carboxylate is not generally considered as a functional group, the plural may either redirect to the article about the parent acid (or the carboxylate if there is a separate article about the carboxylate), or be a separate article or chemistry index that lists salts and esters of the parent acid (e.g. benzoates). Rare cases may have separate articles for the carboxylate, functional group, and group of compounds. Hatnotes should be used to link between these similarly named pages to facilitate navigation between these closely related topics.

Organometallic compounds

The general article about the organometallic chemistry of an element should be entitled "Organo[element] chemistry", e.g., organomercury chemistry, organopalladium chemistry, organozinc chemistry. The IUPAC definition of an "organometallic compound" includes boron, silicon, arsenic, and selenium, so this title guideline also applies to organoboron chemistry, organosilicon chemistry, etc.[6] The related pages "Organo[element] compound" and its plural should generally be redirects. Some flexibility can be used if the article is heavily weighted toward a specific topic, such as the case for organolithium reagent, so long as the other forms redirect there. In some cases, a broad-concept article regarding the organometallic chemistry of an element may not yet exist; in these cases it is adequate to redirect these terms to an appropriate section of another article. On the other hand, depending on the metallic element, it may well be appropriate to have additional articles covering specific compounds or groups of compounds, or specific reactions.

See also


  1. ^ Panico, R.; Powell, W. H. (Eds.) (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-6320-3488-2.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSCIUPAC. ISBN 0-85404-438-8. pp. 47, 248. Electronic version.
  3. ^ Preferred IUPAC Names Provisional Recommendation, September 2004; Chapter 1, par. 16 Name writing, p.80-90
  4. ^ See Longest word in English for more information.
  5. ^ Moss, G.P.; Smith, P.A.S.; Tavernier, D. (1995). "Glossary of Class Names for Organic Compounds and Reactive Intermediates Based on Structure (IUPAC Recommendations 1995)" (PDF). Pure and Applied Chemistry. 67 (8–9): 1307–1375. doi:10.1351/pac199567081307.
  6. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "organometallic compounds". doi:10.1351/goldbook.O04328
General references

External links