|While there is a consensus on describing compounds without fully defined isomerism as groups of isomers, the following text is only a proposal of guidelines in this matter. Is has not been fully accepted as a guideline and any reference to this page should not describe it as containing rules or recommendations.|
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).
|1.||Every chemical compound with fully defined isomerism (cis–trans isomerism; ortho, meta, para isomerism; enantiomerism; etc.) or isotopic composition can be described in a separate item (hereafter item A).||
|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.||
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)).||
|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.|
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).