IUPAC Name questions

Dear ChemAxon,

I have two questions in a file attached.

Kind regards, Paul

Dear Paul,

Thanks for your precise questions. Regarding the first one, both names are officially acceptable as IUPAC names, though indeed it would be better to standardize on one. I contacted IUPAC about this case, because their (draft) specification of the preferred name in this case is unclear.

Regarding the second question, I forwarded the question to our stereo-chemistry expert.

I will let you know when I have further information.

Kind regards,

Daniel

Dear Daniel!

Thank You for answering my questions! Regarding the first one, I do believe that both names are officially acceptable as IUPAC names. The actual question is: why the two equal structures have different names? I can erase CH3 group from one side and put it into symmetrical position – I got the same structure, why do I got different names?

Kind regards, Paul

Dear ChemAxon,

I have found the solution for the first question. The problem of different names can be solved by coping the structure as SMILES, deleting all, and then pasting the structure from the clipboard. From the keyboard:
"Ctrl-A"->"Ctrl-L"->"Ctrl-A"->"Del"->"Ctrl-V"

After that procedure, the two names became equal.

Thank You for help!

Kind regards, Paul

Dear Paul,

Thanks for your update. For case 1, this is indeed a solution. Technically, even 'identical' structures can be represented in several ways internally, possibly leading to different but both valid names. The 'preferred names' specification of IUPAC will take care of that, but it is not complete yet. In the mean time, first making sure the internal representation is identical will guarantee identical names, and exporting to smiles (unique if needed) should make sure of that. This is what you did with the additional copy-paste step.

For case 2, we are working on this issue, and will report when it is fixed.

Best regards,

Daniel

For the second case, the enantiomers are now named (4M)-5-chloro-2,3-dimethylhepta-3,4-diene and (4P)-5-chloro-2,3-dimethylhepta-3,4-diene.

Dear ChemAxon,

I'm really glad the two questions are solved, thank You! The topic can be closed.

Kind regards, Paul