Wikidata:WikiProject Chemistry/Guidelines

Compounds without fully defined isomerism or isotopic compositionEdit

In the following rules structural need is defined as having at least one external identifier to a reliable database (InChI, InChIKey or SMILES are not regarded as such) or at least one valid sitelink to a page on a Wikimedia project (cf. point 1 of Wikidata:Notability).

Inclusion criteriaEdit

1. Every chemical compound with fully defined isomerism (cistrans isomerism; ortho, meta, para isomerism; enantiomerism; etc.) or isotopic composition can be described in a separate item (hereafter item A).
  • (S)-2-pentanol (Q20680358) describes a compound with fully defined stereochemistry (has one stereogenic centre and it is defined). Thus, it can be described in a separate item.
  • 2-Bromobenzaldehyde (Q33859440) describes a compound with defined positions of two substitutents of the benzene ring (ortho position), so it can be described in a separate item.
2. Chemical compound with fully (item B) or partially (item C) undefined isomerism or isotopic composition can be described in a separate item if it fulfils some structural need.
3. Item about a racemic mixture (Q467717) (or more generally: about mixture of isomers) can be described in a separate item (item D) if it fulfils some structural need.
4. Item about a compound being an atropisomer (Q757764) can be described in a separate item if it can be isolated or if it fulfils some structural need.
  • no example yet

Relations between itemsEdit

From the definitions above: item A is about a compound with fully defined isomerism or isotopic composition, item B is about a compound with fully undefined and item C about a compound with partially undefined isomerism or isotopic composition, item D is about a mixture of isomers (usually about a racemic mixture).

5. Item A should always be classified using relation instance of (P31) to item B or item C.
6. Item B and item C should always be classified using relation instance of (P31) to group of chemical compounds (Q56256086) (or one of its subclasses like family of isomeric compounds (Q15711994)).
7. If an item B and an item C exist, the latter should be a subclass of the former (subclass of (P279)).
8. Item A with modified isotopic composition should have a relation instance of (P31) to isotopic compound (Q22332141) (unless it has a relation instance of (P31) to item B or item C that has a relation subclass of (P279) to isotopic compound (Q22332141)).
  • no example yet
9. Items A that are stereoisomers of each other should be linked using stereoisomer of (P3364) property.
10. Item D should be linked to its constituents (items A) using part of (P361) and has part (P527) properties. Item D can be linked to item B or item C using different from (P1889) property if appropriate.

ExamplesEdit

Examples in this section are graphical versions of the examples given above and contains all statements that are required by the above rules.

Example 1: 2-pentanol (two enantiomers)Edit

Following example has three elements: 2-pentanol (Q210479) is an item B (compound with fully undefined stereochemistry) and two enantiomers (items A): (R)-2-pentanol (Q24953060) and (S)-2-pentanol (Q20680358), both has fully defined stereochemistry.

Example 2: nicotine (racemic mixture)Edit

Following example has four elements: nicotine (Q12144) is an item B (compound with fully undefined stereochemistry), (−)-nicotine (Q28086552) and (+)-nicotine (Q27119762) are items B (have fully defined stereochemistry), (±)-nicotine (Q56697247) is a racemic mixture.

Example 3: homocystine (partially defined stereochemistry)Edit

Following example has six elements: DL-homocystine (Q58879461) is an item B (compound with fully undefined stereochemistry), (2S)-homocystine (Q27161892) and (2R)-homocystine (Q58879587) are items C (in both compounds only one of two stereogenic cetres is defined), (2R,2′R)-homocystine (Q58879658), (2S,2′S)-homocystine (Q24188398) and (2R,2′S)-homocystine (Q58879684) are items A (compounds with both stereogenic centres defined).

Example 4: bromobenzaldehyde (ortho, meta, para isomers)Edit

Following example has four items: Bromobenzaldehyde (Q33859433) is an item B (has undefined ortho, meta, para isomerism, i.e. exact positions of substitutents of the benzene ring is not defined), 2-Bromobenzaldehyde (Q33859440), 3-bromobenzaldehyde (Q926392) and 4-bromobenzaldehyde (Q27259983) are items A (are defined isomers).