Not all tautomers generated.

User 81a38f9467

11-10-2010 23:20:37

I drew each of three related tautomers in MarvinSketch (using the online version, which I believe is 5.3.8) and then selected Tools -> Isomers -> Tautomers -> All Tautomers. 

The three compounds are listed here as SMILES:

Compound A: O=C1CC(=NO1)C1=CC=CC=C1
Compound B: O=C1ONC(=C1)C1=CC=CC=C1
Compound C: OC1=CC(=NO1)C1=CC=CC=C1

When I input Compound A, the only tautomer found is Compound A.
When I input B, the only tautomer found is compound B.
When I input C, tautomers B & C are found.

Shouldn't all three tautomers be returned, regardless of which compound is used as the input?


User 851ac690a0

12-10-2010 07:40:13



The ester group (A)  and the aromatic rings (B,C) are protected by the default settings of the tautomerization. This is why these fragments are excluded from the tautomerization.

Optionally , however, both the ester group and the aromatic ring can be activated in the tautomerization process if   the "Protect ester groups"  and the "Protect aromaticity" options are switched off on the options panel. See the attached figure.



User 81a38f9467

12-10-2010 17:50:07


Thank you for the explanation.  I understand this better now.