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dan2097 / opsin

Open Parser for Systematic IUPAC Nomenclature. Chemical name to structure conversion
https://opsin.ch.cam.ac.uk
MIT License
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Possible synonym issue with 4-phenylazophenol #121

Open mjw99 opened 4 years ago

mjw99 commented 4 years ago

With the current https://opsin.ch.cam.ac.uk/ instance, for 4-phenylazophenol , it is returning: C1(=CC=CC=C1)C1=CC(=C(C=C1)O)N=NC1=C(C=CC=C1)O

Sigma have 4-phenylazophenol as the following and note the structures are different.

OPSIN does correctly return with the correct IUPAC name: 4-(Phenyldiazenyl)phenol of what Sigma are returning.

Note, Chemspider lists 4-phenylazophenol as a synonym of 4-(Phenyldiazenyl)phenol .

dan2097 commented 4 years ago

azo nomenclature is nasty as depending on the context it can result in the subsequent ring being implicitly duplicated or just be the substituent -N=N- OPSIN also gives the correct interpretation for 4-(Phenylazo)phenol

I think to disambiguate I would actually need to consider that without locants azophenol is ambiguous, to avoid regressions when interpreting a name like: 4-METHOXY-4'-PHENYLAZOBENZENE https://www.sigmaaldrich.com/catalog/product/aldrich/s949248

rogersayle commented 4 years ago

I'd suggest that "azobenzene" is the special case, and all other uses of "azo" refer to the diazenyl linker. Are there (m)any cases of "azo<ringname>", or even "<locant>,<locant>'-azo<ringname>" in circulation (where <ringname> != benzene)?

p.s. both ChemDraw 19 and Lexichem agree (with Mark) that 2-phenylazophenol has only two rings, but that 4-methoxy-4'-phenylazobenzene has three.

dan2097 commented 4 years ago

azo<ringname> will typically be talking about a class of compounds and is a bit ambigous in meaning. Examples with locants can be easily found for common rings e.g. pyridine, naphthalene. I somewhat agree that benzene is a special case, but only in so much that in most rings all positions are not degenerate.